Rubber composition and pneumatic tire

ABSTRACT

The present invention provides a rubber composition that can enhance the fuel economy, wet-grip performance, abrasion resistance, and processability in a balanced manner, and also provides a pneumatic tire using this rubber composition. The present invention relates to a rubber composition that contains a rubber component, silica, and a compound represented by formula (1) below, wherein the rubber component contains, based on 100% by mass of the rubber component, not less than 5% by mass of a conjugated diene polymer containing a constituent unit based on a conjugated diene and a constituent unit represented by formula (I) below, at least one terminal of the polymer being modified with a specific compound; and an amount of the silica is 5 to 150 parts by mass per 100 parts by mass of the rubber component.

TECHNICAL FIELD

The present invention relates to a rubber composition and a pneumatic tire produced using the rubber composition.

BACKGROUND ART

The demands on automobiles for better fuel economy have been increasing in recent years as concern with environmental issues has been rising. Good fuel economy is also being required of the rubber compositions used for automotive tires. For example, rubber compositions containing a conjugated diene polymer (e.g., polybutadiene, butadiene-styrene copolymer) and a filler (e.g., carbon black, silica) are used for the rubber compositions for automotive tires.

Patent Literature 1, for example, proposes a method for enhancing the fuel economy. This method uses a diene rubber (modified rubber) that has been modified with an organosilicon compound containing an amino group and an alkoxy group. However, the use of the modified rubber may excessively increase the Mooney viscosity and thereby reduce the processability. Meanwhile, wet-grip performance and abrasion resistance are also properties required of the rubber compositions for automotive tires; however, these properties generally assume an inverse relationship with the fuel economy. Thus, a method has been demanded that can enhance the fuel economy, wet-grip performance, abrasion resistance, and processability to high levels in a balanced manner.

Patent Literature 2 proposes a method for enhancing the processability, fuel economy and the like by use of a specific silane coupling agent containing a mercapto group. However, this method still needs to be improved to enhance the fuel economy, wet-grip performance, abrasion resistance, and processability in a balanced manner.

CITATION LIST Patent Literature

Patent Literature 1: JP 2000-344955 A

Patent Literature 2: JP 2009-126907 A

SUMMARY OF INVENTION Technical Problem

An object of the present invention is to solve the problems identified above by providing a rubber composition that provides a well-balanced enhancement of fuel economy, wet-grip performance, abrasion resistance, and processability and by providing a pneumatic tire produced using the rubber composition.

Solution to Problem

The present invention relates to a rubber composition, containing a rubber component, silica, and a compound represented by formula (1) below,

wherein the rubber component contains, based on 100% by mass of the rubber component, not less than 5% by mass of a conjugated diene polymer containing a constituent unit based on a conjugated diene and a constituent unit represented by formula (I) below, at least one terminal of the polymer being modified with at least one compound selected from the group consisting of a compound represented by formula (II) below, a compound containing a group represented by formula (III) below, a compound represented by formula (IV) below, a silicon compound containing at least one of a group represented by formula (V) below and a group represented by formula (VI) below, and a compound containing a group represented by formula (VII) below, and

an amount of the silica is 5 to 150 parts by mass per 100 parts by mass of the rubber component,

wherein X¹, X², and X³ each independently represent a group represented by formula (Ia) below, a hydroxy group, a hydrocarbyl group, or a substituted hydrocarbyl group, and at least one of X¹, X², and X³ is a hydroxy group or a group represented by the following formula (Ia):

wherein R¹ and R² each independently represent a C₁₋₆ hydrocarbyl group, a C₁₋₆ substituted hydrocarbyl group, a silyl group, or a substituted silyl group, and R¹ and R² may be bonded to each other to form a cyclic structure together with the nitrogen atom;

wherein n represents an integer of 1 to 10; R¹¹, R¹², and R¹³ each independently represent a C₁₋₄ hydrocarbyl group or a C₁₋₄ hydrocarbyloxy group, and at least one of R¹¹, R¹², and R¹³ is the hydrocarbyloxy group; and A¹ represents a nitrogen atom-bearing functional group;

wherein p represents an integer of 0 or 1; T represents a C₁₋₂₀ hydrocarbylene group or a C₁₋₂₀ substituted hydrocarbylene group; and A² represents a nitrogen atom-bearing functional group;

wherein g represents an integer of 1 to 10; R²¹ represents a hydrogen atom, a C₁₋₆ hydrocarbyl group, or a C₁₋₆ substituted hydrocarbyl group; A³ represents an oxygen atom or the following group: —NR²²— where R²² represents a hydrogen atom or a C₁₋₁₀ hydrocarbyl group; and A⁴ represents a functional group bearing at least one of a nitrogen atom and an oxygen atom;

wherein w represents an integer of 1 to 11, and A⁵ represents a nitrogen atom-bearing functional group;

wherein R¹⁰¹ represents a hydrogen atom, a branched or unbranched C₁₋₃₀ alkyl group, a branched or unbranched C₂₋₃₀ alkenyl group, a branched or unbranched C₆₋₃₀ aryl group, or a hydroxy group; R¹⁰² and R¹⁰³ are the same as or different from each other and each represent a hydrogen atom, a branched or unbranched C₁₋₃₀ alkyl group, a branched or unbranched C₂₋₃₀ alkenyl group, a branched or unbranched C₂₋₃₀ alkynyl group, a branched or unbranched C₆₋₃₀ aryl group, or a group represented by formula (2) below, wherein a hydrogen atom of the alkyl group, alkenyl group, alkynyl group, or aryl group may be substituted by a hydroxy group or a carboxyl group; a pair of R¹⁰¹ and R¹⁰², a pair of R¹⁰¹ and R¹⁰³, or a pair of R¹⁰² and R¹⁰³ may form a cyclic structure; and d₁ represents an integer of 0 to 8,

wherein R¹⁰⁴ represents a branched or unbranched C₁₋₃₀ alkylene group; R¹⁰⁵ represents a hydrogen atom, a branched or unbranched C₁₋₃₀ alkyl group, a branched or unbranched C₂₋₃₀ alkenyl group, a branched or unbranched C₆₋₃₀ aryl group, or a hydroxy group; and d₂ represents an integer of 0 to 10.

R¹ and R² in formula (Ia) are preferably C₁₋₆ hydrocarbyl groups.

Two of X¹, X², and X³ in formula (I) are preferably selected from a group represented by formula (Ia) and a hydroxy group.

A¹ in formula (II) is preferably a group represented by the following formula (IIa):

wherein R¹⁴ and R¹⁵ each independently represent a C₁₋₆ group optionally containing at least one atom selected from the group consisting of a nitrogen atom, an oxygen atom, and a silicon atom, R¹⁴ and R¹⁵ may be bonded to each other to form a cyclic structure together with the nitrogen atom, and R¹⁴ and R¹⁵ may form a single group bonded to the nitrogen via a double bond.

The group represented by formula (III) is preferably a group represented by the following formula (IIIa):

The compound containing a group represented by formula (III) is preferably at least one compound selected from the group consisting of a compound represented by formula (IIIa-1) below, a compound represented by formula (IIIa-2) below, and a compound represented by formula (IIIa-3) below,

wherein R³¹ represents a hydrogen atom, a C₁₋₁₀ hydrocarbyl group, a C₁₋₁₀ substituted hydrocarbyl group, or a heterocyclic group containing at least one of a nitrogen atom and an oxygen atom as a heteroatom; and R³² and R³³ each independently represent a C₁₋₁₀ group optionally containing at least one atom selected from the group consisting of a nitrogen atom, an oxygen atom, and a silicon atom, R³² and R³³ may be bonded to each other to form a cyclic structure together with the nitrogen atom, and R³² and R³³ may form a single group bonded to the nitrogen via a double bond;

wherein e represents an integer of 0 to 10, and R³⁴ and R³⁵ each independently represent a C₁₋₂₀ hydrocarbyl group or a C₁₋₂₀ substituted hydrocarbyl group;

wherein f represents an integer of 0 to 10, and R³⁶ represents a C₁₋₂₀ hydrocarbyl group or a C₁₋₂₀ substituted hydrocarbyl group.

The compound containing a group represented by formula (III) is preferably a compound represented by the following formula (IIIb-1):

wherein R³⁷ represents a hydrogen atom, a C₁₋₁₀ hydrocarbyl group, a C₁₋₁₀ substituted hydrocarbyl group, or a heterocyclic group containing at least one of a nitrogen atom and an oxygen atom as a heteroatom; R³⁸ and R³⁹ each independently represent a C₁₋₁₀ group optionally containing at least one atom selected from the group consisting of a nitrogen atom, an oxygen atom, and a silicon atom, R³⁸ and R³⁹ may be bonded to each other to form a cyclic structure together with the nitrogen atom, and R³⁸ and R³⁹ may form a single group bonded to the nitrogen via a double bond; and T represents a C₁₋₂₀ hydrocarbylene group or a C₁₋₂₀ substituted hydrocarbylene group.

The compound represented by formula (IIIb-1) is preferably at least one compound selected from the group consisting of a compound represented by formula (IIIb-1-1) below, and a compound represented by formula (IIIb-1-2) below,

wherein r represents an integer of 1 or 2; and Y¹ represents a nitrogen atom-bearing functional group that is a substituent on the benzene ring, and when a plurality of Y¹'s are present, the plurality of Y¹'s may be the same as or different from one another;

wherein s represents an integer of 1 or 2; t represents an integer of 0 to 2; Y² and Y³ each represent a nitrogen atom-bearing functional group that is a substituent on the benzene ring, and when a plurality of Y²'s are present, the plurality of Y²'s may be the same as or different from one another, and when a plurality of Y³'s are present, the plurality of Y³'s may be the same as or different from one another.

A⁴ in formula (IV) is preferably a hydroxy group or a group represented by the following formula (IVa):

wherein R²³ and R²⁴ each independently represent a C₁₋₆ group optionally containing at least one atom selected from the group consisting of a nitrogen atom, an oxygen atom, and a silicon atom, R²³ and R²⁴ may be bonded to each other to form a cyclic structure together with the nitrogen atom, and R²³ and R²⁴ may form a single group bonded to the nitrogen via a double bond.

The silicon compound preferably contains a group represented by the following formula (VIII):

wherein R⁴¹, R⁴², and R⁴³ each independently represent a C₁₋₄ hydrocarbyl group or a C₁₋₄ hydrocarbyloxy group, and at least one of R⁴¹, R⁴², and R⁴³ is the hydrocarbyloxy group.

The silicon compound preferably contains a group represented by the following formula (Va):

wherein h represents an integer of 1 to 10, and R⁴⁴, R⁴⁵, and R⁴⁶ each independently represent a C₁₋₄ hydrocarbyl group or a C₁₋₄ hydrocarbyloxy group, and at least one of R⁴⁴, R⁴⁵, and R⁴⁶ is the hydrocarbyloxy group.

The compound containing a group represented by formula (VII) is preferably a compound represented by the following formula (VII-1):

wherein z represents an integer of 0 to 10; R⁷¹ represents a C₁₋₅ hydrocarbyl group; R⁷², R⁷³, R⁷⁴ and R⁷⁵ each independently represent a hydrogen atom, a C₁₋₅ hydrocarbyl group, a C₁₋₅ substituted hydrocarbyl group, or a C₁₋₅ hydrocarbyloxy group, and when a plurality of R⁷²'s and a plurality of R⁷³'s are present, the plurality of R⁷²'s and the plurality of R⁷³'s may be the same as or different from one another; and R⁷⁶ and R⁷⁷ each independently represent a C₁₋₆ group optionally containing at least one atom selected from the group consisting of a nitrogen atom, an oxygen atom, and a silicon atom, R⁷⁶ and R⁷⁷ may be bonded to each other to form a cyclic structure together with the nitrogen atom, and R⁷⁶ and R⁷⁷ may form a single group bonded to the nitrogen via a double bond.

One of R⁷⁴ and R⁷⁵ in formula (VII-1) is preferably a hydrogen atom.

The conjugated diene polymer preferably has a vinyl bond content of at least 10 mol % but not more than 80 mol % per 100 mol % of the constituent unit based on a conjugated diene.

Preferably, the rubber composition contains at least one of natural rubber and butadiene rubber.

The silica preferably has a nitrogen adsorption specific surface area of 40 to 400 m²/g.

An amount of the compound represented by formula (1) is preferably 0.1 to 20 parts by mass per 100 parts by mass of silica.

The rubber composition is preferably for use as a rubber composition for a tread.

The present invention also relates to a pneumatic tire, produced using the foregoing rubber composition.

Advantageous Effects of Invention

The present invention relates to a rubber composition including a specific conjugated diene polymer, silica, and a compound represented by the above formula (1). Thus, the present invention can provide a pneumatic tire that is improved in fuel economy, wet-grip performance, abrasion resistance, and processability in a balanced manner.

DESCRIPTION OF EMBODIMENTS

The rubber composition of the present invention contains silica, a compound represented by the above formula (1), and a conjugated diene polymer containing a constituent unit based on a conjugated diene and a constituent unit represented by formula (I) below, at least one terminal of the polymer being modified with at least one compound selected from the group consisting of a compound represented by formula (II) below, a compound containing a group represented by formula (III) below, a compound represented by formula (IV) below, a silicon compound containing a group represented by formula (V) below and/or a group represented by formula (VI) below, and a compound containing a group represented by formula (VII) below.

In the formula, X¹, X², and X³ each independently represent a group represented by formula (Ia) below, a hydroxy group, a hydrocarbyl group, or a substituted hydrocarbyl group, and at least one of X¹, X², and X³ is a hydroxy group or a group represented by the following formula (Ia):

wherein R¹ and R² each independently represent a C₁₋₆ hydrocarbyl group, a C₁₋₆ substituted hydrocarbyl group, a silyl group, or a substituted silyl group, and R¹ and R² may be bonded to each other to form a cyclic structure together with the nitrogen atom.

In the formula, n represents an integer of 1 to 10; R¹¹, R¹², and R¹³ each independently represent a C₁₋₄ hydrocarbyl group or a C₁₋₄ hydrocarbyloxy group, and at least one of R¹¹, R¹², and R¹³ is the hydrocarbyloxy group; and A¹ represents a nitrogen atom-bearing functional group.

In the formula, p represents an integer of 0 or 1; T represents a C₁₋₂₀ hydrocarbylene group or a C₁₋₂₀ substituted hydrocarbylene group; and A² represents a nitrogen atom-bearing functional group.

In the formula, g represents an integer of 1 to 10; R²¹ represents a hydrogen atom, a C₁₋₆ hydrocarbyl group, or a C₁₋₆ substituted hydrocarbyl group; A³ represents an oxygen atom or the following group: —NR²²— where R²² represents a hydrogen atom or a C₁₋₁₀ hydrocarbyl group; and A⁴ represents a functional group bearing a nitrogen atom and/or an oxygen atom.

In the formula, w represents an integer of 1 to 11, and A⁵ represents a nitrogen atom-bearing functional group.

The conjugated dienes for the conjugated diene-based constituent unit can be exemplified by 1,3-butadiene, isoprene, 1,3-pentadiene, 2,3-dimethyl-1,3-butadiene, and 1,3-hexadiene, and one, or two or more of these may be used. Preferred are 1,3-butadiene and isoprene, in view of ease of availability.

X¹, X², and X³ in formula (I) of the constituent unit represented by formula (I) each independently represent a group represented by formula (Ia), a hydroxy group, a hydrocarbyl group, or a substituted hydrocarbyl group, and at least one of X¹, X², and X³ is a group represented by formula (Ia) or a hydroxy group.

R¹ and R² in formula (Ia) each independently represent a C₁₋₆ hydrocarbyl group, a C₁₋₆ substituted hydrocarbyl group, a silyl group, or a substituted silyl group, and R¹ and R² may be bonded to each other to form a cyclic structure together with the nitrogen atom.

As used herein, the term “hydrocarbyl group” denotes a monovalent hydrocarbon residue. This hydrocarbon residue refers to a group obtained by removing hydrogen from a hydrocarbon. The term “substituted hydrocarbyl group” denotes a group obtained by substituting one or more hydrogen atoms of a monovalent hydrocarbon residue by substituent groups. The term “hydrocarbyloxy group” denotes a group obtained by substituting the hydrogen atom of a hydroxyl group by a hydrocarbyl group. The term “substituted hydrocarbyloxy group” denotes a group obtained by substituting one or more hydrogen atoms of a hydrocarbyloxy group by substituent groups. The term “hydrocarbylene group” denotes a divalent hydrocarbon residue. The term “substituted hydrocarbylene group” denotes a group obtained by substituting one or more hydrogen atoms of a divalent hydrocarbon residue by substituent groups. The term “substituted silyl group” denotes a group obtained by substituting one or more hydrogen atoms of a silyl group by substituent groups.

The C₁₋₆ hydrocarbyl groups encompassed by R¹ and R² can be exemplified by alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, n-pentyl, neopentyl, isopentyl, and n-hexyl groups; cycloalkyl groups such as a cyclohexyl group; and a phenyl group.

The C₁₋₆ substituted hydrocarbyl groups encompassed by R¹ and R² can be exemplified by substituted hydrocarbyl groups containing as a substituent at least one group selected from the group consisting of nitrogen atom-bearing groups, oxygen atom-bearing groups, and silicon atom-bearing groups. The groups containing a nitrogen atom-bearing group as a substituent can be exemplified by dialkylaminoalkyl groups such as dimethylaminoethyl and diethylaminoethyl groups. The groups containing an oxygen atom-bearing group as a substituent can be exemplified by alkoxyalkyl groups such as methoxymethyl, methoxyethyl, ethoxymethyl, and ethoxyethyl groups. The groups containing a silicon atom-bearing group as a substituent can be exemplified by trialkylsilylalkyl groups such as a trimethylsilylmethyl group.

The substituted silyl groups encompassed by R¹ and R² can be exemplified by trialkylsilyl groups such as trimethylsilyl, triethylsilyl, and t-butyldimethylsilyl groups.

The groups in which R¹ and R² are bonded to each other can be exemplified by C₁₋₁₂ divalent groups optionally containing at least one atom selected from the group consisting of a nitrogen atom, an oxygen atom, and a silicon atom. Specific examples thereof include alkylene groups such as trimethylene, tetramethylene, pentamethylene, and hexamethylene groups; oxydialkylene groups such as oxydiethylene and oxydipropylene groups; and nitrogenous groups such as a group represented by —CH₂CH₂—NH—CH₂— and a group represented by —CH₂CH₂—N═CH—.

The group in which R¹ and R² are bonded to each other is preferably a nitrogenous group, and more preferably a group represented by —CH₂CH₂—NH—CH₂— or a group represented by —CH₂CH₂—N═CH—.

The hydrocarbyl group encompassed by R¹ and R² is preferably an alkyl group, more preferably a C₁₋₄ alkyl group, further preferably a methyl group, an ethyl group, an n-propyl group, or an n-butyl group, and particularly preferably an ethyl group or an n-butyl group. The substituted hydrocarbyl group encompassed by R¹ and R² is preferably an alkoxyalkyl group, and more preferably a C₁₋₄ alkoxyalkyl group. The substituted silyl group encompassed by R¹ and R² is preferably a trialkylsilyl group, and more preferably a trimethylsilyl group.

Preferably, R¹ and R² are a nitrogenous group in which R¹ and R² are bonded to each other, or are each independently an alkyl group, an alkoxyalkyl group, or a substituted silyl group, more preferably an alkyl group, still more preferably a C₁₋₄ alkyl group, and further preferably a methyl group, an ethyl group, an n-propyl group, or an n-butyl group.

The group represented by formula (Ia) may be an acyclic amino group or a cyclic amino group.

The acyclic amino groups can be exemplified by dialkylamino groups such as dimethylamino, diethylamino, di(n-propyl)amino, di(isopropyl)amino, di(n-butyl)amino, di(sec-butyl)amino, di(tert-butyl)amino, di(neopentyl)amino, and ethylmethylamino groups; di(alkoxyalkyl)amino groups such as di(methoxymethyl)amino, di(methoxyethyl)amino, di(ethoxymethyl)amino, and di(ethoxyethyl)amino groups; and di(trialkylsilyl)amino groups such as di(trimethylsilyl)amino and di(t-butyldimethylsilyl) amino groups.

The cyclic amino groups can be exemplified by 1-polymethyleneimino groups such as 1-pyrrolidinyl, 1-piperidino, 1-hexamethyleneimino, 1-heptamethyleneimino, 1-octamethyleneimino, 1-decamethyleneimino, and 1-dodecamethyleneimino groups. The cyclic amino groups can also be exemplified by 1-imidazolyl, 4,5-dihydro-1-imidazolyl, 1-imidazolidinyl, 1-piperazinyl, and morpholino groups.

In view of economic efficiency and ease of availability, the group represented by formula (Ia) is preferably an acyclic amino group, more preferably a dialkylamino group, still more preferably a dialkylamino group which contains a C₁₋₄ alkyl group as a substituent, and further preferably a dimethylamino group, a diethylamino group, a di(n-propyl)amino group, or a di(n-butyl)amino group.

The hydrocarbyl groups encompassed by X¹, X², and X³ in formula (I) can be exemplified by alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, and tert-butyl groups. The substituted hydrocarbyl groups can be exemplified by alkoxyalkyl groups such as methoxymethyl, ethoxymethyl, methoxyethyl, and ethoxyethyl groups.

The hydrocarbyl group encompassed by X¹, X², and X³ is preferably an alkyl group, more preferably a C₁₋₄ alkyl group, and still more preferably a methyl group or an ethyl group. The substituted hydrocarbyl group encompassed by X¹, X², and X³ is preferably an alkoxyalkyl group, and more preferably a C₁₋₄ alkoxyalkyl group.

The hydrocarbyl group or substituted hydrocarbyl group encompassed by X¹, X², and X³ is preferably an alkyl group or an alkoxyalkyl group, more preferably a C₁₋₄ alkyl group or a C₁₋₄ alkoxyalkyl group, still more preferably a C₁₋₄ alkyl group, and further preferably a methyl group or an ethyl group.

At least one of X¹, X², and X³ in formula (I) is a hydroxy group or a group represented by formula (Ia).

Preferably at least two of X¹, X², and X³ are each a hydroxy group or a group represented by formula (Ia), and more preferably two of X¹, X², and X³ are each a hydroxy group or a group represented by formula (Ia). In view of achieving the fuel economy, wet-grip performance, abrasion resistance, and processability at high levels in a balanced manner, preferably at least one of X¹, X², and X³ is a hydroxy group, more preferably at least two of X¹, X², and X³ are hydroxy groups, and still more preferably two of X¹, X² and X³ are hydroxy groups.

In view of enhancing the fuel economy, wet-grip performance, abrasion resistance, and processability in a balanced manner, the constituent unit represented by formula (I) is preferably a constituent unit in which two of X¹, X², and X³ are, independently, an acyclic amino group or a hydroxy group. The constituent unit in which two of X¹, X², and X³ are acyclic amino groups is preferably a bis(dialkylamino)alkylvinylsilane unit and is more preferably a bis(dimethylamino)methylvinylsilane unit, bis(diethylamino)methylvinylsilane unit, bis(di(n-propyl)amino)methylvinylsilane unit, or bis(di(n-butyl)amino)methylvinylsilane unit. The constituent unit in which two of X¹, X², and X³ are hydroxy groups is preferably a dihydroxyalkylvinylsilane unit, and more preferably a dihydroxymethylvinylsilane unit.

In view of enhancing the fuel economy, wet-grip performance, abrasion resistance, and processability in a balanced manner, the content of the constituent unit represented by formula (I) in the conjugated diene polymer, expressed per unit mass of the polymer, is preferably at least 0.001 mmol/g-polymer but not more than 0.1 mmol/g-polymer, more preferably at least 0.002 mmol/g-polymer but not more than 0.07 mmol/g-polymer, and even more preferably at least 0.003 mmol/g-polymer but not more than 0.05 mmol/g-polymer.

At least one terminal of the conjugated diene polymer is modified with a specific compound (modifying agent 1 to 5). This causes interaction with silica, thereby enhancing the fuel economy, wet-grip performance, abrasion resistance, and processability in a balanced manner.

The following explains the compound (modifying agent 1) represented by formula (II) below.

In the formula, n represents an integer of 1 to 10; R¹¹, R¹², and R¹³ each independently represent a C₁₋₄ hydrocarbyl group or a C₁₋₄ hydrocarbyloxy group, and at least one of R¹¹, R¹², and R¹³ is the hydrocarbyloxy group; and A¹ represents a nitrogen atom-bearing functional group.

R¹¹, R¹², and R¹³ in formula (II) each independently represent a C₁₋₄ hydrocarbyl group or a C₁₋₄ hydrocarbyloxy group, and at least one of R¹¹, R¹², and R¹³ is the hydrocarbyloxy group.

The hydrocarbyl groups encompassed by R¹¹, R¹², and R¹³ can be exemplified by alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, and tert-butyl groups. The hydrocarbyloxy groups encompassed by R¹¹, R¹², and R¹³ can be exemplified by alkoxy groups such as methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, sec-butoxy, and t-butoxy groups.

The hydrocarbyl group encompassed by R¹¹, R¹², and R¹³ is preferably an alkyl group, more preferably a C₁₋₃ alkyl group, and still more preferably a methyl group or, an ethyl group. The hydrocarbyloxy group encompassed by R¹¹, R¹², and R¹³ is preferably an alkoxy group, more preferably a C₁₋₃ alkoxy group, and still more preferably a methoxy group or an ethoxy group.

In view of enhancing the fuel economy, wet-grip performance, abrasion resistance, and processability in a balanced manner, preferably at least two of R¹¹, R¹², and R¹³ are hydrocarbyloxy groups, and more preferably the three of R¹¹, R¹², and R¹³ are hydrocarbyloxy groups.

In formula (II), n represents an integer of 1 to 10. In view of enhancing the fuel economy, wet-grip performance, abrasion resistance, and processability in a balanced manner, n is preferably not less than 3. In view of enhancing the economic efficiency, n is preferably not more than 4. Particularly preferably, n is 3.

A¹ in formula (II) is a nitrogen atom-bearing functional group and examples include amino, isocyano, cyano, pyridyl, piperidyl, pyrazinyl, and morpholino groups.

A¹ is preferably a group represented by the following formula (IIa).

In the formula, R¹⁴ and R¹⁵ each independently represent a C₁₋₆ group optionally containing at least one atom selected from the group consisting of a nitrogen atom, an oxygen atom, and a silicon atom; R¹⁴ and R¹⁵ may be bonded to each other to form a cyclic structure together with the nitrogen atom; and R¹⁴ and R¹⁵ may form a single group bonded to the nitrogen via a double bond.

Examples of R¹⁴ and R¹⁵ in formula (IIa) include C₁₋₆ hydrocarbyl groups, C₁₋₆ substituted hydrocarbyl groups, and substituted silyl groups.

The hydrocarbyl groups encompassed by R¹⁴ and R¹⁵ can be exemplified by alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, n-pentyl, neopentyl, isopentyl, and n-hexyl groups; cycloalkyl groups such as a cyclohexyl group; and a phenyl group.

The substituted hydrocarbyl groups encompassed by and R¹⁵ can be exemplified by substituted hydrocarbyl groups containing as a substituent at least one group selected from the group consisting of nitrogen atom-bearing groups, oxygen atom-bearing groups, and silicon atom-bearing groups. The groups containing a nitrogen atom-bearing group as a substituent can be exemplified by dialkylaminoalkyl groups such as dimethylaminoethyl and diethylaminoethyl groups. The groups containing an oxygen atom-bearing group as a substituent can be exemplified by alkoxyalkyl groups such as methoxymethyl, methoxyethyl, ethoxymethyl, and ethoxyethyl groups; alkylene oxide groups such as epoxy and tetrahydrofuranyl groups; and alkylene oxide alkyl groups such as glycidyl and tetrahydrofurfuryl groups. The groups containing a silicon atom-bearing group as a substituent can be exemplified by trialkylsilylalkyl groups such as a trimethylsilylmethyl group.

As used herein, the term “alkylene oxide group” denotes a monovalent group obtained by removing a hydrogen atom from the ring of a cyclic ether compound. The term “alkylene oxide alkyl group” denotes a group obtained by substituting at least one hydrogen atom of an alkyl group by an alkylene oxide group.

The substituted silyl groups encompassed by R¹⁴ and R¹⁵ can be exemplified by trialkylsilyl groups such as trimethylsilyl, triethylsilyl, and t-butyldimethylsilyl groups, and trialkoxysilyl groups such as a trimethoxysilyl group.

The groups in which R¹⁴ and R¹⁵ are bonded to each other can be exemplified by C₂₋₁₂ divalent groups optionally containing at least one atom selected from the group consisting of a nitrogen atom, an oxygen atom, and a silicon atom. Specific examples thereof include alkylene groups such as trimethylene, tetramethylene, pentamethylene, and hexamethylene groups; oxydialkylene groups such as oxydiethylene and oxydipropylene groups; and nitrogenous groups such as a group represented by —CH₂CH₂—NH—CH₂— and a group represented by —CH₂CH₂—N═CH—.

The group in which R¹⁴ and R¹⁵ are bonded to each other is preferably a nitrogenous group, and more preferably a group represented by —CH₂CH₂—NH—CH₂— or a group represented by —CH₂CH₂—N═CH—.

Examples of the single group bonded to the nitrogen via a double bond, formed by R¹⁴ and R¹⁵, include C₂₋₁₂ divalent groups optionally containing at least one atom selected from the group consisting of a nitrogen atom, an oxygen atom, and a silicon atom. Specific examples thereof include an ethylidene group, a 1-methylpropylidene group, a 1,3-dimethylbutylidene group, a 1-methylethylidene group, and a 4-N,N-dimethylaminobenzylidene group.

The hydrocarbyl group encompassed by R¹⁴ and R¹⁵ is preferably an alkyl, group, more preferably a C₁₋₄ alkyl group, still more preferably a methyl group, an ethyl group, an n-propyl group, or an n-butyl group, and further preferably a methyl group or an ethyl group. The substituted hydrocarbyl group encompassed by R¹⁴ and R¹⁵ is preferably an alkoxyalkyl group, an alkylene oxide group, or an alkylene oxide alkyl group. The substituted silyl group encompassed by R¹⁴ and R¹⁵ is preferably a trialkylsilyl group or a trialkoxysilyl group, more preferably a trialkylsilyl group, and still more preferably a trimethylsilyl group or a triethylsilyl group.

Preferably, R¹⁴ and R¹⁵ are a nitrogenous group in which R¹⁴ and R¹⁵ are bonded to each other, or are each independently an alkyl group, an alkoxyalkyl group, an alkylene oxide group, an alkylene oxide alkyl group, or a substituted silyl group, more preferably an alkyl group, an alkylene oxide group, an alkylene oxide alkyl group, or a trialkylsilyl group.

The groups represented by formula (IIa) can be exemplified by acyclic amino groups and cyclic amino groups.

Examples of the acyclic amino groups include dialkylamino groups such as dimethylamino, diethylamino, di(n-propyl)amino, di(isopropyl)amino, di(n-butyl)amino, di(sec-butyl)amino, di(tert-butyl)amino, di(neopentyl)amino, and ethylmethylamino groups; di(alkoxyalkyl)amino groups such as di(methoxymethyl)amino, di(methoxyethyl)amino, di(ethoxymethyl)amino, and di(ethoxyethyl)amino groups; and di(trialkylsilyl)amino groups such as di(trimethylsilyl)amino and di(t-butyldimethylsilyl)amino groups. Other examples include di(alkylene oxide)amino groups such as di(epoxy)amino and di(tetrahydrofuranyl)amino groups; and di(alkylene oxide alkyl)amino groups such as di(glycidyl)amino and di(tetrahydrofurfuryl)amino groups. Additional examples include ethylideneamino, 1-methylpropylideneamino, 1,3-dimethylbutylideneamino, 1-methylethylideneamino, and 4-N,N-dimethylaminobenzylideneamino groups.

As used herein, the term “di(alkylene oxide)amino group” denotes an amino group in which two hydrogen atoms bonded to the nitrogen atom are substituted by two alkylene oxide groups. The term “di(alkylene oxide alkyl)amino group” denotes an amino group in which two hydrogen atoms bonded to the nitrogen atom are substituted by two alkylene oxide alkyl groups.

The cyclic amino groups can be exemplified by 1-polymethyleneimino groups such as 1-pyrrolidinyl, 1-piperidino, 1-hexamethyleneimino, 1-heptamethyleneimino, 1-octamethyleneimino, 1-decamethyleneimino, and 1-dodecamethyleneimino groups. The cyclic amino groups can also be exemplified by 1-imidazolyl, 4,5-dihydro-1-imidazolyl, 1-imidazolidinyl, 1-piperazinyl, and morpholino groups.

In view of fuel economy, wet-grip performance, abrasion resistance, processability, and long-term stability and easy availability of the compound, the group represented by formula (IIa) is preferably an acyclic amino group, and more preferably a dialkylamino group, a di(alkylene oxide)amino group, a di(alkylene oxide alkyl)amino group, or a di(trialkylsilyl)amino group.

The compounds represented by formula (II) can be exemplified by compounds in which formula (IIa) is an acyclic amino group such as a dialkylamino group, a di(alkoxyalkyl)amino group, a di(alkylene oxide)amino group, a di(alkylene oxide alkyl)amino group, or a trialkylsilyl group.

The compounds in which formula (IIa) is a dialkylamino group can be exemplified by the following:

-   [3-(dialkylamino)propyl]trialkoxysilanes such as -   [3-(dimethylamino)propyl]trimethoxysilane, -   [3-(diethylamino)propyl]trimethoxysilane, -   [3-(ethylmethylamino)propyl]trimethoxysilane, -   [3-(dimethylamino)propyl]triethoxysilane, -   [3-(diethylamino)propyl]triethoxysilane, and -   [3-(ethylmethylamino)propyl]triethoxysilane; -   [3-(dialkylamino)propyl]alkyldialkoxysilanes such as -   [3-(dimethylamino)propyl]methyldimethoxysilane, -   [3-(diethylamino)propyl]methyldimethoxysilane, -   [3-(ethylmethylamino)propyl]methyldimethoxysilane, -   [3-(dimethylamino)propyl]ethyldimethoxysilane, -   [3-(diethylamino)propyl]ethyldimethoxysilane, -   [3-(ethylmethylamino)propyl]ethyldimethoxysilane, -   [3-(dimethylamino)propyl]methyldiethoxysilane, -   [3-(diethylamino)propyl]methyldiethoxysilane, -   [3-(ethylmethylamino)propyl]methyldiethoxysilane, -   [3-(dimethylamino)propyl]ethyldiethoxysilane, -   [3-(diethylamino)propyl]ethyldiethoxysilane, and -   [3-(ethylmethylamino)propyl]ethyldiethoxysilane; and -   [3-(dialkylamino)propyl]dialkylalkoxysilanes such as -   [3-(dimethylamino)propyl]dimethylmethoxysilane, -   [3-(diethylamino)propyl]dimethylmethoxysilane, -   [3-(dimethylamino)propyl]diethylmethoxysilane, -   [3-(diethylamino)propyl]diethylmethoxysilane, -   [3-(dimethylamino)propyl]dimethylethoxysilane, -   [3-(diethylamino)propyl]dimethylethoxysilane, -   [3-(dimethylamino)propyl]diethylethoxysilane, and -   [3-(diethylamino)propyl]diethylethoxysilane.

The compounds in which formula (IIa) is a di(alkoxyalkyl)amino group can be exemplified by the following:

-   {3-[di(alkoxyalkyl)amino]propyl}trialkoxysilanes such as -   {3-[di(methoxymethyl)amino]propyl}trimethoxysilane, -   {3-[di(ethoxymethyl)amino]propyl}trimethoxysilane, -   {3-[di(methoxyethyl)amino]propyl}trimethoxysilane, -   {3-[di(ethoxyethyl)amino]propyl}trimethoxysilane, -   {3-[di(methoxymethyl)amino]propyl}triethoxysilane, -   {3-[di(ethoxymethyl)amino]propyl}triethoxysilane, -   {3-[di(methoxyethyl)amino]propyl}triethoxysilane, and -   {3-[di(ethoxyethyl)amino]propyl}triethoxysilane; -   {3-[di(alkoxyalkyl)amino]propyl}alkyldialkoxysilanes such as -   {3-[di(methoxymethyl)amino]propyl}methyldimethoxysilane, -   {3-[di(ethoxymethyl)amino]propyl}methyldimethoxysilane, -   {3-[di(methoxyethyl)amino]propyl}methyldimethoxysilane, -   {3-[di(ethoxyethyl)amino]propyl}methyldimethoxysilane, -   {3-[di(methoxymethyl)amino]propyl}ethyldimethoxysilane, -   {3-[di(ethoxymethyl)amino]propyl}ethyldimethoxysilane, -   {3-[di(methoxyethyl)amino]propyl}ethyldimethoxysilane, -   {3-[di(ethoxyethyl)amino]propyl}ethyldimethoxysilane, -   {3-[di(methoxymethyl)amino]propyl}methyldiethoxysilane, -   {3-[di(ethoxymethyl)amino]propyl}methyldiethoxysilane, -   {3-[di(methoxyethyl)amino]propyl}methyldiethoxysilane, -   {3-[di(ethoxyethyl)amino]propyl}methyldiethoxysilane, -   {3-[di(methoxymethyl)amino]propyl}ethyldiethoxysilane, -   {3-[di(ethoxymethyl)amino]propyl}ethyldiethoxysilane, -   {3-[di(methoxyethyl)amino]propyl}ethyldiethoxysilane, and -   {3-[di(ethoxyethyl)amino]propyl}ethyldiethoxysilane; and -   {3-[di(alkoxyalkyl)amino]propyl}dialkylalkoxysilanes such as -   {3-[di(methoxymethyl)amino]propyl}dimethylmethoxysilane, -   {3-[di(ethoxymethyl)amino]propyl}dimethylmethoxysilane, -   {3-[di(methoxyethyl)amino]propyl}dimethylmethoxysilane, -   {3-[di(ethoxyethyl)amino]propyl}dimethylmethoxysilane, -   {3-[di(methoxymethyl)amino]propyl}diethylmethoxysilane, -   {3-[di(ethoxymethyl)amino]propyl}diethylmethoxysilane, -   {3-[di(methoxyethyl)amino]propyl}diethylmethoxysilane, -   {3-[di(ethoxyethyl)amino]propyl}diethylmethoxysilane, -   {3-[di(methoxymethyl)amino]propyl}dimethylethoxysilane, -   {3-[di(ethoxymethyl)amino]propyl}dimethylethoxysilane, -   {3-[di(methoxyethyl)amino]propyl}dimethylethoxysilane, -   {3-[di(ethoxyethyl)amino]propyl}dimethylethoxysilane, -   {3-[di(methoxymethyl)amino]propyl}diethylethoxysilane, -   {3-[di(ethoxymethyl)amino]propyl}diethylethoxysilane, -   {3-[di(methoxyethyl)amino]propyl}diethylethoxysilane, and -   {3-[di(ethoxyethyl)amino]propyl}diethylethoxysilane.

The compounds in which formula (IIa) is a di(alkylene oxide)amino group can be exemplified by compounds in which formula (IIa) is a di(epoxy)amino group, such as

-   {3-[di(epoxy)amino]propyl}trimethoxysilane, -   {3-[di(epoxy)amino]propyl}triethoxysilane, -   {3-[di(epoxy)amino]propyl}methyldimethoxysilane, -   {3-[di(epoxy)amino]propyl}ethyldimethoxysilane, -   {3-[di(epoxy)amino]propyl}methyldiethoxysilane, -   {3-[di(epoxy)amino]propyl}ethyldiethoxysilane, -   {3-[di(epoxy)amino]propyl}dimethylmethoxysilane, -   {3-[di(epoxy)amino]propyl}diethylmethoxysilane, -   {3-[di(epoxy)amino]propyl}dimethylethoxysilane, and -   {3-[di(epoxy)amino]propyl}diethylethoxysilane; and

compounds in which formula (IIa) is a di(tetrahydrofuranyl)amino group, such as

-   {3-[di(tetrahydrofuranyl)amino]propyl}trimethoxysilane, -   {3-[di(tetrahydrofuranyl)amino]propyl}triethoxysilane, -   {3-[di(tetrahydrofuranyl)amino]propyl}-methyldimethoxysilane, -   {3-[di(tetrahydrofuranyl)amino]propyl}-ethyldimethoxysilane, -   {3-[di(tetrahydrofuranyl)amino]propyl}-methyldiethoxysilane, -   {3-[di(tetrahydrofuranyl)amino]propyl}-ethyldiethoxysilane, -   {3-[di(tetrahydrofuranyl)amino]propyl}-dimethylmethoxysilane, -   {3-[di(tetrahydrofuranyl)amino]propyl}-diethylmethoxysilane, -   {3-[di(tetrahydrofuranyl)amino]propyl}-dimethylethoxysilane, and -   {3-[di(tetrahydrofuranyl)amino]propyl}-diethylethoxysilane.

The compounds in which formula (IIa) is a di(alkylene oxide alkyl)amino group can be exemplified by compounds in which formula (IIa) is a di(glycidyl)amino group, such as

-   {3-[di(glycidyl)amino]propyl}trimethoxysilane, -   {3-[di(glycidyl)amino]propyl}triethoxysilane, -   {3-[di(glycidyl)amino]propyl}methyldimethoxysilane, -   {3-[di(glycidyl)amino]propyl}ethyldimethoxysilane, -   {3-[di(glycidyl)amino]propyl}methyldiethoxysilane, -   {3-[di(glycidyl)amino]propyl}ethyldiethoxysilane, -   {3-[di(glycidyl)amino]propyl}dimethylmethoxysilane, -   {3-[di(glycidyl)amino]propyl}diethylmethoxysilane, -   {3-[di(glycidyl)amino]propyl}dimethylethoxysilane, and -   {3-[di(glycidyl)amino]propyl}diethylethoxysilane; and

compounds in which formula (IIa) is a

di(tetrahydrofurfuryl)amino group, such as

-   {3-[di(tetrahydrofurfuryl)amino]propyl}trimethoxysilane, -   {3-[di(tetrahydrofurfuryl)amino]propyl}triethoxysilane, -   {3-[di(tetrahydrofurfuryl)amino]propyl}-methyldimethoxysilane, -   {3-[di(tetrahydrofurfuryl)amino]propyl}-ethyldimethoxysilane, -   {3-[di(tetrahydrofurfuryl)amino]propyl}-methyldiethoxysilane, -   {3-[di(tetrahydrofurfuryl)amino]propyl}-ethyldiethoxysilane, -   {3-[di(tetrahydrofurfuryl)amino]propyl}-dimethylmethoxysilane, -   {3-[di(tetrahydrofurfuryl)amino]propyl}-diethylmethoxysilane, -   {3-[di(tetrahydrofurfuryl)amino]propyl}-dimethylethoxysilane, and -   {3-[di(tetrahydrofurfuryl)amino]propyl}-diethylethoxysilane.

The compounds in which formula (IIa) is a trialkylsilyl group can be exemplified by the following:

-   {3-[di(trialkylsilyl)amino]propyl}trialkoxysilanes such as -   {3-[di(trimethylsilyl)amino]propyl}trimethoxysilane, -   {3-[di(t-butyldimethylsilyl)amino]propyl}-trimethoxysilane, -   {3-[di(trimethylsilyl)amino]propyl}triethoxysilane, and -   {3-[di(t-butyldimethylsilyl)amino]propyl}-triethoxysilane; -   {3-[di(trialkylsilyl)amino]propyl}alkyldialkoxysilanes such as -   {3-[di(trimethylsilyl)amino]propyl}methyldimethoxysilane, -   {3-[di(t-butyldimethylsilyl)amino]propyl}-methyldimethoxysilane, -   {3-[di(trimethylsilyl)amino]propyl}methyldiethoxysilane, and -   {3-[di(t-butyldimethylsilyl)amino]propyl}-methyldiethoxysilane; and -   {3-[di(trialkylsilyl)amino]propyl}dialkylalkoxysilanes such as -   {3-[di(trimethylsilyl)amino]propyl}dimethylmethoxysilane, -   {3-[di(t-butyldimethylsilyl)amino]propyl}-dimethylmethoxysilane, -   {3-[di(trimethylsilyl)amino]propyl}dimethylethoxysilane, and -   {3-[di(t-butyldimethylsilyl)amino]propyl}-dimethylethoxysilane.

Preferred among the preceding are [3-(dialkylamino)propyl]trialkoxysilanes, and more preferred are [3-(dimethylamino)propyl]trimethoxysilane,

-   [3-(diethylamino)propyl]trimethoxysilane, -   [3-(dimethylamino)propyl]triethoxysilane, and -   [3-(diethylamino)propyl]triethoxysilane.

The compounds represented by formula (II) can also be exemplified by compounds in which formula (IIa) is a cyclic amino group such as a 1-piperidino group, a 1-hexamethyleneimino group, a 1-imidazolyl group, a 4,5-dihydro-1-imidazolyl group, a 1-piperazinyl group, or a morpholino group.

The compounds in which formula (IIa) is a 1-piperidino group can be exemplified by

-   3-(1-piperidino)propyltrimethoxysilane, -   3-(1-piperidino)propyltriethoxysilane, -   3-(1-piperidino)propylmethyldimethoxysilane, -   3-(1-piperidino)propylethyldimethoxysilane, -   3-(1-piperidino)propylmethyldiethoxysilane, and -   3-(1-piperidino)propylethyldiethoxysilane.

The compounds in which formula (IIa) is a 1-hexamethyleneimino group can be exemplified by

-   3-(1-hexamethyleneimino)propyltrimethoxysilane, -   3-(1-hexamethyleneimino)propyltriethoxysilane, -   3-(1-hexamethyleneimino)propylmethyldimethoxysilane, -   3-(1-hexamethyleneimino)propylethyldimethoxysilane, -   3-(1-hexamethyleneimino)propylmethyldiethoxysilane, and -   3-(1-hexamethyleneimino)propylethyldiethoxysilane.

The compounds in which formula (IIa) is a 1-imidazolyl group can be exemplified by

-   N-(3-trimethoxysilylpropyl)imidazole and -   N-(3-triethoxysilylpropyl)imidazole.

The compounds in which formula (IIa) is a 4,5-dihydro-1-imidazolyl group can be exemplified by

-   N-(3-trimethoxysilylpropyl)-4,5-dihydroimidazole and -   N-(3-triethoxysilylpropyl)-4,5-dihydroimidazole.

The compounds in which formula (IIa) is a 1-piperazinyl group can be exemplified by

-   3-(1-piperazinyl)propyltrimethoxysilane, -   3-(1-piperazinyl)propyltriethoxysilane, -   3-(1-piperazinyl)propylmethyldimethoxysilane, -   3-(1-piperazinyl)propylethyldimethoxysilane, -   3-(1-piperazinyl)propylmethyldiethoxysilane, and -   3-(1-piperazinyl)propylethyldiethoxysilane.

The compounds in which formula (IIa) is a morpholino group can be exemplified by

-   3-morpholinopropyltrimethoxysilane, -   3-morpholinopropyltriethoxysilane, -   3-morpholinopropylmethyldimethoxysilane, -   3-morpholinopropylethyldimethoxysilane, -   3-morpholinopropylmethyldiethoxysilane, and -   3-morpholinopropylethyldiethoxysilane.

Among the preceding, compounds in which formula (IIa) is a 1-imidazolyl group and compounds in which formula (IIa) is a 4,5-dihydro-1-imidazolyl group are preferred, and N-(3-trimethoxysilylpropyl)imidazole,

-   N-(3-triethoxysilylpropyl)imidazole, -   N-(3-trimethoxysilylpropyl)-4,5-dihydroimidazole, and -   N-(3-triethoxysilylpropyl)-4,5-dihydroimidazole are more preferred.

The following explains the compound (modifying agent 2) containing a group represented by formula (III) below.

In the formula, p represents an integer of 0 or 1; T represents a C₁₋₂₀ hydrocarbylene group or a C₁₋₂₀ substituted hydrocarbylene group; and A² represents a nitrogen atom-bearing functional group.

Here, p represents an integer of 0 or 1. T represents a C₁₋₂₀ hydrocarbylene group or a C₁₋₂₀ substituted hydrocarbylene group. A² represents a nitrogen atom-bearing functional group and examples include amino, isocyano, cyano, pyridyl, piperidyl, pyrazinyl, and morpholino groups.

The compounds containing a group represented by formula (III) can be exemplified by compounds containing a group represented by formula (III) in which p is 0 and A² is an amino group, namely, the following formula (IIIa).

Examples of the compounds containing a group represented by formula (IIIa) include carboxylic acid amide compounds such as formamide, acetamide, and propionamide. Other examples include cyclic compounds such as imidazolidinone and derivatives thereof and lactams.

The compounds containing a group represented by formula (IIIa) can be exemplified by carboxylic acid amide compounds represented by the following formula (IIIa-1):

wherein R³¹ represents a hydrogen atom, a C₁₋₁₀ hydrocarbyl group, a C₁₋₁₀ substituted hydrocarbyl group, or a heterocyclic group containing a nitrogen atom and/or an oxygen atom as a heteroatom; and R³² and R³³ each independently represent a C₁₋₁₀ group optionally containing at least one atom selected from the group consisting of a nitrogen atom, an oxygen atom, and a silicon atom, R³² and R³³ may be bonded to each other to form a cyclic structure together with the nitrogen atom, and R³² and R³³ may form a single group bonded to the nitrogen via a double bond.

The hydrocarbyl groups encompassed by R³¹ can be exemplified by alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, and t-butyl groups; aryl groups such as phenyl, methylphenyl, ethylphenyl, and naphthyl groups; and aralkyl groups such as a benzyl group.

The substituted hydrocarbyl groups encompassed by R³¹ can be exemplified by substituted hydrocarbyl groups containing as a substituent at least one group selected from the group consisting of nitrogen atom-bearing groups and oxygen atom-bearing groups. The groups containing a nitrogen atom-bearing group as a substituent can be exemplified by dialkylaminoalkyl groups such as dimethylaminoethyl and diethylaminoethyl groups. The groups containing an oxygen atom-bearing group as a substituent can be exemplified by alkoxyalkyl groups such as methoxymethyl, methoxyethyl, ethoxymethyl, and ethoxyethyl groups.

The heterocyclic group containing a nitrogen atom and/or an oxygen atom as a heteroatom, encompassed by R³¹, refers to a residue of a heterocyclic compound that contains a nitrogen atom and/or an oxygen atom in the ring. Such groups can be exemplified by a 2-pyridyl group, a 3-pyridyl group, a 4-pyridyl group, and a 2-furyl group.

R³¹ is preferably a C₁₋₁₀ hydrocarbyl group or a C₁₋₁₀ substituted hydrocarbyl group, more preferably a C₁₋₄ alkyl group, and particularly preferably a methyl group, an ethyl group, an n-propyl group, or an n-butyl group.

Examples of R³² and R³³ in formula (IIIa-1) include C₁₋₁₀ hydrocarbyl groups and C₁₋₁₀ substituted hydrocarbyl groups. The hydrocarbyl groups encompassed by R³² and R³³ can be exemplified by alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, and t-butyl groups; aryl groups such as phenyl, methylphenyl, ethylphenyl, and naphthyl groups; and aralkyl groups such as a benzyl group.

The substituted hydrocarbyl groups encompassed by R³² and R³³ can be exemplified by substituted hydrocarbyl groups containing as a substituent at least one group selected from the group consisting of nitrogen atom-bearing groups and oxygen atom-bearing groups. The groups containing a nitrogen atom-bearing group as a substituent can be exemplified by dialkylaminoalkyl groups such as dimethylaminoethyl and diethylaminoethyl groups. The groups containing an oxygen atom-bearing group as a substituent can be exemplified by alkoxyalkyl groups such as methoxymethyl, methoxyethyl, ethoxymethyl, and ethoxyethyl groups.

The groups in which R³² and R³³ are bonded to each other can be exemplified by C₂₋₂₀ divalent groups optionally containing at least one atom selected from the group consisting of a nitrogen atom, an oxygen atom, and a silicon atom. Specific examples thereof include alkylene groups such as trimethylene, tetramethylene, pentamethylene, and hexamethylene groups; oxydialkylene groups such as oxydiethylene and oxydipropylene groups; and nitrogenous groups such as a group represented by —CH₂CH₂—NH—CH₂— and a group represented by —CH₂CH₂—N═CH—.

Examples of the single group bonded to the nitrogen via a double bond, formed by R³² and R³³, include C₂₋₁₂ divalent groups optionally containing at least one atom selected from the group consisting of a nitrogen atom and an oxygen atom. Specific examples thereof include an ethylidene group, a 1-methylpropylidene group, a 1,3-dimethylbutylidene group, a 1-methylethylidene group, and a 4-N,N-dimethylaminobenzylidene group.

R³² and R³³ are each independently preferably a hydrocarbyl group, more preferably an alkyl group, still more preferably a C₁₋₄ alkyl group, and particularly preferably a methyl group, an ethyl group, an n-propyl group, or an n-butyl group.

The carboxylic acid amide compounds represented by formula (IIIa-1) can be exemplified by formamide compounds such as formamide, N,N-dimethylformamide, and N,N-diethylformamide;

acetamide compounds such as acetamide, N,N-dimethylacetamide, N,N-diethylacetamide, aminoacetamide, N,N-dimethyl-N′,N′-dimethylaminoacetamide, N,N-dimethylaminoacetamide, N-ethylaminoacetamide, N,N-dimethyl-N′-ethylaminoacetamide, N,N-dimethylaminoacetamide, and N-phenyldiacetamide;

propionamide compounds such as propionamide and N,N-dimethylpropionamide;

pyridylamide compounds such as 4-pyridylamide and N,N-dimethyl-4-pyridylamide;

benzamide compounds such as benzamide, N,N-dimethylbenzamide, N′,N′-(p-dimethylamino)benzamide, N′,N′-(p-diethylamino)benzamide, N,N-dimethyl-N′,N′-(p-dimethylamino)benzamide, and N,N-dimethyl-N′,N′-(p-diethylamino)benzamide;

acrylamide compounds such as N,N-dimethylacrylamide and N,N-diethylacrylamide;

methacrylamide compounds such as N,N-dimethylmethacrylamide and N,N-diethylmethacrylamide;

nicotinamide compounds such as N,N-dimethylnicotinamide and N,N-diethylnicotinamide;

phthalamide compounds such as N,N,N′,N′-tetramethylphthalamide and N,N,N′,N′-tetraethylphthalamide; and

phthalimide compounds such as N-methylphthalimide and N-ethylphthalimide.

The cyclic compounds containing a group represented by formula (IIIa) can be exemplified by compounds represented by the following formula (IIIa-2) and compounds represented by the following formula (IIIa-3).

In the formula, e represents an integer of 0 to 10, and R³⁴ and R³⁵ each independently represent a C₁₋₂₀ hydrocarbyl group or a C₁₋₂₀ substituted hydrocarbyl group.

In the formula, f represents an integer of 0 to 10, and R³⁶ represents a C₁₋₂₀ hydrocarbyl group or a C₁₋₂₀ substituted hydrocarbyl group.

R³⁴, R³⁵, and R³⁶ in formulas (IIIa-2) and (IIIa-3) each independently represent a C₁₋₂₀ hydrocarbyl group or a C₁₋₂₀ substituted hydrocarbyl group. The hydrocarbyl groups encompassed by R³⁴, R³⁵, and R³⁶ can be exemplified by alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, and t-butyl groups; aryl groups such as phenyl, methylphenyl, ethylphenyl, and naphthyl groups; and aralkyl groups such as a benzyl group.

The substituted hydrocarbyl groups encompassed by R³⁴, R³⁵, and R³⁶ can be exemplified by substituted hydrocarbyl groups containing as a substituent at least one group selected from the group consisting of nitrogen atom-bearing groups, oxygen atom-bearing groups, and silicon atom-bearing groups. The groups containing a nitrogen atom-bearing group as a substituent can be exemplified by dialkylaminoalkyl groups such as dimethylaminoethyl and diethylaminoethyl groups. The groups containing an oxygen atom-bearing group as a substituent can be exemplified by alkoxyalkyl groups such as methoxymethyl, methoxyethyl, ethoxymethyl, and ethoxyethyl groups; and alkoxyaryl groups such as methoxyphenyl and ethoxyphenyl groups. The groups containing a silicon atom-bearing group as a substituent can be exemplified by trimethylsilylmethyl, t-butyldimethylsilyloxymethyl, and trimethoxysilylpropyl groups.

R³⁴ and R³⁵ in formula (IIIa-2) are each independently preferably a hydrocarbyl group, more preferably an alkyl group, and still more preferably a methyl group.

R³⁶ in formula (IIIa-3) is preferably a hydrocarbyl group, more preferably an alkyl group or an aryl group, and still more preferably a methyl group or a phenyl group.

In formulas (IIIa-2) and (IIIa-3), e and f each represent an integer of 0 to 10. Here, e and f are each independently preferably not less than 2 in view of enhancing the fuel economy, wet-grip performance, abrasion resistance, and processability in a balanced manner, whereas e and f are each independently preferably not more than 7 in view of enhancing the economic efficiency of the production.

The compounds represented by formula (IIIa-2) can be exemplified by 1,3-hydrocarbyl-substituted 2-imidazolidinones such as 1,3-dimethyl-2-imidazolidinone, 1,3-diethyl-2-imidazolidinone, 1,3-di(n-propyl)-2-imidazolidinone, 1,3-di(t-butyl)-2-imidazolidinone, and 1,3-diphenyl-2-imidazolidinone. The compound represented by formula (IIIa-2) is preferably a 1,3-substituted 2-imidazolidinone, more preferably a 1,3-hydrocarbyl-substituted 2-imidazolidinone, and still more preferably a 1,3-dialkyl-2-imidazolidinone. The 1,3-dialkyl-2-imidazolidinone is preferably 1,3-dimethyl-2-imidazolidinone, 1,3-diethyl-2-imidazolidinone, or 1,3-di(n-propyl)-2-imidazolidinone, and more preferably 1,3-dimethyl-2-imidazolidinone.

The compounds represented by formula (IIIa-3) can be exemplified by the following:

β-propiolactam compounds such as N-methyl-β-propiolactam, N-(t-butyl)-β-propiolactam, and N-phenyl-β-propiolactam;

2-pyrrolidone compounds such as 1-methyl-2-pyrrolidone, 1-(t-butyl)-2-pyrrolidone, 1-phenyl-2-pyrrolidone, 1-(p-methylphenyl)-2-pyrrolidone, 1-(p-methoxyphenyl)-2-pyrrolidone, 1-benzyl-2-pyrrolidone, 1-naphthyl-2-pyrrolidone, 1-phenyl-5-methyl-2-pyrrolidone, 1-(t-butyl)-5-methyl-2-pyrrolidone, and 1-(t-butyl)-1,3-dimethyl-2-pyrrolidone;

2-piperidone compounds such as 1-(t-butyl)-2-piperidone, 1-phenyl-2-piperidone, 1-(p-methylphenyl)-2-piperidone, 1-(p-methoxyphenyl)-2-piperidone, and 1-naphthyl-2-piperidone;

ε-caprolactam compounds such as N-methyl-ε-caprolactam, N-ethyl-ε-caprolactam, N-(n-propyl)-ε-caprolactam, N-phenyl-ε-caprolactam, N-(p-methoxyphenyl)-ε-caprolactam, and N-benzyl-ε-caprolactam; and

ω-laurylolactam compounds such as N-phenyl-ω-laurylolactam.

The compound represented by formula (IIIa-3) is preferably a 2-pyrrolidone compound or an ε-caprolactam compound, more preferably a 1-hydrocarbyl-substituted 2-pyrrolidone or an N-hydrocarbyl-substituted ε-caprolactam, still more preferably a 1-alkyl-substituted 2-pyrrolidone, a 1-aryl-substituted 2-pyrrolidone, an N-alkyl-substituted ε-caprolactam, or an N-aryl-substituted ε-caprolactam, and particularly preferably 1-phenyl-2-pyrrolidone or N-methyl-ε-caprolactam.

The compounds containing a group represented by formula (III) can also be exemplified by compounds containing a group represented by formula (III) in which p is 1 and A² is an amino group, namely, the following formula (IIIb).

In the formula, T represents a C₁₋₂₀ hydrocarbylene group or a C₁₋₂₀ substituted hydrocarbylene group.

The compounds containing a group represented by formula (IIIb) can be exemplified by benzaldehyde compounds, acetophenone compounds, and benzophenone compounds.

The compounds containing a group represented by formula (IIIb) can also be exemplified by compounds represented by the following formula (IIIb-1):

wherein R³⁷ represents a hydrogen atom, a C₁₋₁₀ hydrocarbyl group, a C₁₋₁₀ substituted hydrocarbyl group, or a heterocyclic group containing a nitrogen atom and/or an oxygen atom as a heteroatom; R³⁸ and R³⁹ each independently represent a C₁₋₁₀ group optionally containing at least one atom selected from the group consisting of a nitrogen atom, an oxygen atom, and a silicon atom, R³⁸ and R³⁹ may be bonded to each other to form a cyclic structure together with the nitrogen atom, and R³⁸ and R³⁹ may form a single group bonded to the nitrogen via a double bond; and T represents a C₁₋₂₀ hydrocarbylene group or a C₁₋₂₀ substituted hydrocarbylene group.

The hydrocarbyl groups encompassed by R³⁷ can be exemplified by alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, and t-butyl groups; aryl groups such as phenyl, methylphenyl, ethylphenyl, and naphthyl groups; and aralkyl groups such as a benzyl group.

The substituted hydrocarbyl groups encompassed by R³⁷ can be exemplified by substituted hydrocarbyl groups containing as a substituent at least one group selected from the group consisting of nitrogen atom-bearing groups and oxygen atom-bearing groups. The groups containing a nitrogen atom-bearing group as a substituent can be exemplified by dialkylaminoalkyl groups such as dimethylaminoethyl and diethylaminoethyl groups. The groups containing an oxygen atom-bearing group as a substituent can be exemplified by alkoxyalkyl groups such as methoxymethyl, methoxyethyl, ethoxymethyl, and ethoxyethyl groups.

The heterocyclic group containing a nitrogen atom and/or an oxygen atom as a heteroatom, encompassed by R³⁷, refers to a residue of a heterocyclic compound that contains a nitrogen atom and/or an oxygen atom in the ring, and such groups can be exemplified by a 2-pyridyl group, a 3-pyridyl group, a 4-pyridyl group, and a 2-furyl group.

R³⁷ is preferably a hydrogen atom, a C₁₋₁₀ hydrocarbyl group, or a C₁₋₁₀ substituted hydrocarbyl group. The C₁₋₁₀ hydrocarbyl group is preferably a C₁₋₄ alkyl group or a phenyl group, and particularly preferably a methyl group, an ethyl group, an n-propyl group, an n-butyl group, or a phenyl group. The C₁₋₁₀ substituted hydrocarbyl group is preferably an aryl group containing a nitrogen atom-bearing group as a substituent, and more preferably a dialkylaminophenyl group or a 4-morpholinophenyl group.

Examples of R³⁸ and R³⁹ in formula (IIIb-1) include C₁₋₁₀ hydrocarbyl groups and C₁₋₁₀ substituted hydrocarbyl groups.

The hydrocarbyl groups encompassed by R³⁸ and R³⁹ can be exemplified by alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, and t-butyl groups; aryl groups such as phenyl, methylphenyl, ethylphenyl, and naphthyl groups; and aralkyl groups such as a benzyl group.

The substituted hydrocarbyl groups encompassed by R³⁸ and R³⁹ can be exemplified by substituted hydrocarbyl groups containing as a substituent at least one group selected from the group consisting of nitrogen atom-bearing groups and oxygen atom-bearing groups. The groups containing a nitrogen atom-bearing group as a substituent can be exemplified by dialkylaminoalkyl groups such as dimethylaminoethyl and diethylaminoethyl groups. The groups containing an oxygen atom-bearing group as a substituent can be exemplified by alkoxyalkyl groups such as methoxymethyl, methoxyethyl, ethoxymethyl, and ethoxyethyl groups.

The groups in which R³⁸ and R³⁹ are bonded to each other can be exemplified by C₂₋₂₀ divalent groups optionally containing at least one atom selected from the group consisting of a nitrogen atom, an oxygen atom, and a silicon atom. Specific examples thereof include alkylene groups such as trimethylene, tetramethylene, pentamethylene, and hexamethylene groups; oxydialkylene groups such as oxydiethylene and oxydipropylene groups; and nitrogenous groups such as a group represented by —CH₂CH₂—NH—CH₂— and a group represented by —CH₂CH₂—N═CH—.

Examples of the single group bonded to the nitrogen via a double bond, formed by R³⁸ and R³⁹, include C₂₋₁₂ divalent groups optionally containing at least one atom selected from the group consisting of a nitrogen atom and an oxygen atom. Specific examples thereof include an ethylidene group, a 1-methylpropylidene group, a 1,3-dimethylbutylidene group, a 1-methylethylidene group, and a 4-N,N-dimethylaminobenzylidene group.

R³³ and R³⁹ are each independently preferably a hydrocarbyl group, more preferably an alkyl group, still more preferably a C₁₋₄ alkyl group, and particularly preferably a methyl group, an ethyl group, an n-propyl group, or an n-butyl group.

The hydrocarbylene groups encompassed by T can be exemplified by alkylene groups such as methylene, ethylene, trimethylene, tetramethylene, pentamethylene, and hexamethylene groups; and arylene groups such as phenylene, methylphenylene, ethylphenylene, and naphthylene groups.

The substituted hydrocarbylene groups encompassed by T can be exemplified by substituted hydrocarbylene groups containing as a substituent at least one group selected from the group consisting of nitrogen atom-bearing groups and oxygen atom-bearing groups. The groups containing a nitrogen atom-bearing group as a substituent can be exemplified by dialkylaminoalkylene groups such as dimethylaminoethylene and diethylaminoethylene groups; and dialkylaminoarylene groups such as dimethylaminophenylene and diethylaminophenylene groups. The groups containing an oxygen atom-bearing group as a substituent can be exemplified by alkoxyalkylene groups such as methoxymethylene, methoxyethylene, ethoxymethylene, and ethoxyethylene groups.

T is preferably a hydrocarbylene group, more preferably an arylene group, and still more preferably a phenylene group.

The compounds represented by formula (IIIb-1) can be exemplified by dialkylamino-substituted benzaldehyde compounds such as 4-dimethylaminobenzaldehyde, 4-diethylaminobenzaldehyde, and 3,5-bis(dihexylamino)-benzaldehyde; dialkylamino-substituted acetophenone compounds such as 4-dimethylaminoacetophenone and 4-diethylaminoacetophenone; heterocyclic group-substituted acetophenone compounds such as 4-morpholinoacetophenone, 4′-imidazol-1-yl-acetophenone, and 4-pyrazolylacetophenone; dialkylamino-substituted benzophenone compounds such as 4,4′-bis(dimethylamino)benzophenone, 4,4′-bis(diethylamino)-benzophenone, 4-dimethylaminobenzophenone, 4-diethylaminobenzophenone, 3-dimethylaminobenzophenone, and 3-diethylaminobenzophenone; and heterocyclic group-substituted benzophenone compounds such as 4-morpholinobenzophenone, 4′-(imidazol-1-yl)benzophenone, and 4-pyrazolylbenzophenone.

The compound represented by formula (IIIb-1) is preferably a substituted acetophenone compound or a substituted benzophenone compound, and examples thereof include compounds represented by the following formula (IIIb-1-1) and compounds represented by the following formula (IIIb-1-2):

wherein r represents an integer of 1 or 2; and Y¹ represents a nitrogen atom-bearing functional group that is a substituent on the benzene ring, and when a plurality of Y¹'s are present, the plurality of Y¹'s may be the same as or different from one another;

wherein s represents an integer of 1 or 2; t represents an integer of 0 to 2; and Y² and Y³ each represent a nitrogen atom-bearing functional group that is a substituent on the benzene ring, and when a plurality of Y²'s are present, the plurality of Y²'s may be the same as or different from one another, and when a plurality of Y³'s are present, the plurality of Y³'s may be the same as or different from one another.

Y¹, Y², and Y³ in formulas (IIIb-1-1) and (IIIb-1-2) represent nitrogen atom-bearing functional groups and examples thereof include amino, isocyano, cyano, pyridyl, piperidyl, pyrazinyl, pyrimidinyl, pyrrolyl, imidazolyl, pyrazolyl, and morpholino groups. Dialkylamino, imidazolyl, and morpholino groups are preferred. The alkyl of the dialkylamino group is preferably a C₁₋₁₀ alkyl group.

The compound represented by formula (IIIb-1) is more preferably a heterocyclic group-substituted acetophenone compound, a dialkylamino-substituted benzophenone compound, or a heterocyclic group-substituted benzophenone compound and is particularly preferably 4′-imidazol-1-yl-acetophenone, 4-morpholinoacetophenone, 4-dimethylaminobenzophenone, 4-diethylaminobenzophenone, 4,4′-bis(dimethylamino)benzophenone, 4,4′-bis(diethylamino)-benzophenone, or 4-morpholinobenzophenone.

The following explains the compound (modifying agent 3) represented by formula (IV) below.

In the formula, g represents an integer of 1 to 10; R²¹ represents a hydrogen atom, a C₁₋₆ hydrocarbyl group, or a C₁₋₆ substituted hydrocarbyl group; A³ represents an oxygen atom or the following group: —NR²²— where R²² represents a hydrogen atom or a C₁₋₁₀ hydrocarbyl group; and A⁴ represents a functional group bearing a nitrogen atom and/or an oxygen atom.

Here, g represents an integer of 1 to 10. In view of enhancing the fuel economy, wet-grip performance, abrasion resistance, and processability in a balanced manner, g is preferably not less than 2. In view of enhancing the economic efficiency of the production, g is preferably not more than 4. Particularly preferably, g is 3.

R²¹ in formula (IV) represents a hydrogen atom, a C₁₋₆ hydrocarbyl group, or a C₁₋₆ substituted hydrocarbyl group.

The hydrocarbyl groups encompassed by R²¹ can be exemplified by alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, and t-butyl groups.

The substituted hydrocarbyl groups encompassed by R²¹ can be exemplified by substituted hydrocarbyl groups containing as a substituent at least one group selected from the group consisting of nitrogen atom-bearing groups, oxygen atom-bearing groups, and silicon atom-bearing groups. The groups containing a nitrogen atom-bearing group as a substituent can be exemplified by dialkylaminoalkyl groups such as dimethylaminoethyl and diethylaminoethyl groups. The groups containing an oxygen atom-bearing group as a substituent can be exemplified by alkoxyalkyl groups such as methoxymethyl, methoxyethyl, ethoxymethyl, and ethoxyethyl groups. The groups containing a silicon atom-bearing group as a substituent can be exemplified by trialkylsilylalkyl groups such as a trimethylsilylmethyl group; trialkylsilyloxyalkyl groups such as a t-butyldimethylsilyloxymethyl group; and trialkoxysilylalkyl groups such as a trimethoxysilylpropyl group.

The hydrocarbyl group encompassed by R²¹ is preferably an alkyl group, more preferably a C₁₋₄ alkyl group, still more preferably a methyl group or an ethyl group, and further preferably a methyl group. The substituted hydrocarbyl group encompassed by R²¹ is preferably an alkoxyalkyl group, more preferably a C₁₋₄ alkoxyalkyl group, still more preferably a methoxymethyl group or an ethoxyethyl group, and further preferably a methoxymethyl group.

In view of economic efficiency and in view of enhancing the fuel economy, wet-grip performance, abrasion resistance, and processability in a balanced manner, R²¹ is preferably a hydrogen atom, an alkyl group, or an alkoxyalkyl group, more preferably a hydrogen atom, a C₁₋₄ alkyl group, or a C₁₋₄ alkoxyalkyl group, still more preferably a hydrogen atom, a methyl group, or a methoxymethyl group, and further preferably a hydrogen atom or a methyl group.

A³ in formula (IV) represents an oxygen atom or the following group: —NR²²— where R²² represents a hydrogen atom or a C₁₋₁₀ hydrocarbyl group.

The hydrocarbyl groups encompassed by R²² can be exemplified by alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, and t-butyl groups; aryl groups such as phenyl, methylphenyl, ethylphenyl, and naphthyl groups; and aralkyl groups such as a benzyl group.

The hydrocarbyl group encompassed by R²² is preferably an alkyl group, more preferably a C₁₋₄ alkyl group, and still more preferably a methyl group or an ethyl group.

R²² is preferably a hydrogen atom or an alkyl group, more preferably a hydrogen atom or a C₁₋₄ alkyl group, still more preferably a hydrogen atom, a methyl group, or an ethyl group, and further preferably a hydrogen atom or a methyl group.

A⁴ in formula (IV) represents a functional group bearing a nitrogen atom and/or an oxygen atom. Examples of the nitrogen atom-bearing functional group include amino, isocyano, cyano, pyridyl, piperidyl, piperazinyl, and morpholino groups.

Examples of the oxygen atom-bearing functional group include alkoxy groups such as methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, sec-butoxy, and t-butoxy groups; alkoxyalkyl groups such as methoxymethyl, methoxyethyl, ethoxymethyl, and ethoxyethyl groups; alkoxyaryl groups such as methoxyphenyl and ethoxyphenyl groups; and alkylene oxide groups such as epoxy and tetrahydrofuranyl groups. Other examples include trialkylsilyloxy groups such as trimethylsilyloxy, triethylsilyloxy, and t-butyldimethylsilyloxy groups. Additional examples include a hydroxy group.

A⁴ is preferably a hydroxy group or a group represented by formula (IVa) below, and more preferably a group represented by the following formula (IVa):

wherein R²³ and R²⁴ each independently represent a C₁₋₆ group optionally containing at least one atom selected from the group consisting of a nitrogen atom, an oxygen atom, and a silicon atom, R²³ and R²⁴ may be bonded to each other to form a cyclic structure together with the nitrogen atom, and R²³ and R²⁴ may form a single group bonded to the nitrogen via a double bond.

Examples of R²³ and R²⁴ in formula (IVa) include C₁₋₆ hydrocarbyl groups, C₁₋₆ substituted hydrocarbyl groups, and substituted silyl groups.

The hydrocarbyl groups encompassed by R²³ and R²⁴ can be exemplified by alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, n-pentyl, neopentyl, isopentyl, and n-hexyl groups; cycloalkyl groups such as a cyclohexyl group; and a phenyl group.

The substituted hydrocarbyl groups encompassed by R²³ and R²⁴ can be exemplified by substituted hydrocarbyl groups containing as a substituent at least one group selected from the group consisting of nitrogen atom-bearing groups, oxygen atom-bearing groups, and silicon atom-bearing groups. The groups containing a nitrogen atom-bearing group as a substituent can be exemplified by dialkylaminoalkyl groups such as dimethylaminoethyl and diethylaminoethyl groups. The groups containing an oxygen atom-bearing group as a substituent can be exemplified by alkoxyalkyl groups such as methoxymethyl, methoxyethyl, ethoxymethyl, and ethoxyethyl groups; alkylene oxide groups such as epoxy and tetrahydrofuranyl groups; and alkylene oxide alkyl groups such as glycidyl and tetrahydrofurfuryl groups. The groups containing a silicon atom-bearing group as a substituent can be exemplified by trialkylsilylalkyl groups such as a trimethylsilylmethyl group.

As used herein, the term “alkylene oxide group” denotes a monovalent group obtained by removing a hydrogen atom from the ring of a cyclic ether compound. The term “alkylene oxide alkyl group” denotes a group obtained by substituting at least one hydrogen atom of an alkyl group by an alkylene oxide group.

The substituted silyl groups encompassed by R²³ and R²⁴ can be exemplified by trialkylsilyl groups such as trimethylsilyl, triethylsilyl, and t-butyldimethylsilyl groups; and trialkoxysilyl groups such as a trimethoxysilyl group.

The groups in which R²³ and R²⁴ are bonded to each other can be exemplified by C₂₋₁₂ divalent groups optionally containing at least one atom selected from the group consisting of a nitrogen atom, an oxygen atom, and a silicon atom. Specific examples thereof include alkylene groups such as trimethylene, tetramethylene, pentamethylene, and hexamethylene groups; oxydialkylene groups such as oxydiethylene and oxydipropylene groups; and nitrogenous groups such as a group represented by —CH₂CH₂—NH—CH₂— and a group represented by —CH₂CH₂—N═CH—.

The group in which R²³ and R²⁴ are bonded to each other is preferably a nitrogenous group, and more preferably a group represented by —CH₂CH₂—NH—CH₂— or a group represented by —CH₂CH₂—N═CH—.

Examples of the single group bonded to the nitrogen via a double bond, formed by R²³ and R²⁴, include C₂₋₁₂ divalent groups optionally containing at least one atom selected from the group consisting of a nitrogen atom, an oxygen atom, and a silicon atom. Specific examples thereof include an ethylidene group, a 1-methylpropylidene group, a 1,3-dimethylbutylidene group, a 1-methylethylidene group, and a 4-N,N-dimethylaminobenzylidene group.

The hydrocarbyl group encompassed by R²³ and R²⁴ is preferably an alkyl group, more preferably a C₁₋₄ alkyl group, still more preferably a methyl group, an ethyl group, an n-propyl group, or an n-butyl group, and further preferably a methyl group or an ethyl group. The substituted hydrocarbyl group encompassed by R²³ and R²⁴ is preferably an alkoxyalkyl group, an alkylene oxide group, or an alkylene oxide alkyl group. The substituted silyl group encompassed by R²³ and R²⁴ is preferably a trialkylsilyl group or a trialkoxysilyl group, more preferably a trialkylsilyl group, and still more preferably a trimethylsilyl group or a triethylsilyl group.

Preferably, R²³ and R²⁴ are a nitrogenous group in which R²³ and R²⁴ are bonded to each other, or are each independently an alkyl group, an alkoxyalkyl group, an alkylene oxide group, an alkylene oxide alkyl group, or a substituted silyl group, more preferably an alkyl group, an alkylene oxide group, an alkylene oxide alkyl group, or a trialkylsilyl group.

The groups represented by formula (IVa) can be exemplified by acyclic amino groups and cyclic amino groups.

Examples of the acyclic amino groups include dialkylamino groups such as dimethylamino, diethylamino, di(n-propyl)amino, di(isopropyl)amino, di(n-butyl)amino, di(sec-butyl)amino, di(tert-butyl)amino, di(neopentyl)amino, and ethylmethylamino groups; di(alkoxyalkyl)amino groups such as di(methoxymethyl)amino, di(methoxyethyl)amino, di(ethoxymethyl)amino, and di(ethoxyethyl)amino groups; and di(trialkylsilyl)amino groups such as di(trimethylsilyl)amino and di(t-butyldimethylsilyl)amino groups. Other examples include di(alkylene oxide)amino groups such as di(epoxy)amino and di(tetrahydrofuranyl)amino groups; and di(alkylene oxide alkyl)amino groups such as di(glycidyl)amino and di(tetrahydrofurfuryl)amino groups. Additional examples include ethylideneamino, 1-methylpropylideneamino, 1,3-dimethylbutylideneamino, 1-methylethylideneamino, and 4-N,N-dimethylaminobenzylideneamino groups.

As used herein, the term “di(alkylene oxide)amino group” denotes an amino group in which two hydrogen atoms bonded to the nitrogen atom are substituted by two alkylene oxide groups. The term “di(alkylene oxide alkyl)amino group” denotes an amino group in which two hydrogen atoms bonded to the nitrogen atom are substituted by two alkylene oxide alkyl groups.

The cyclic amino groups can be exemplified by 1-polymethyleneimino groups such as 1-pyrrolidinyl, 1-piperidino, 1-hexamethyleneimino, 1-heptamethyleneimino, 1-octamethyleneimino, 1-decamethyleneimino, and 1-dodecamethyleneimino groups. The cyclic amino groups can also be exemplified by 1-imidazolyl, 4,5-dihydro-1-imidazolyl, 1-imidazolidinyl, 1-piperazinyl, and morpholino groups.

In view of fuel economy, wet-grip performance, abrasion resistance, processability, and long-term stability and easy availability of the compound, the group represented by formula (IVa) is preferably an acyclic amino group, and is more preferably a dialkylamino group, a di(alkylene oxide)amino group, a di(alkylene oxide alkyl)amino group, or a di(trialkylsilyl)amino group.

The compounds represented by formula (IV) can be exemplified by compounds in which A³ is a secondary amino group, such as acrylamide compounds and methacrylamide compounds.

The acrylamide compounds in which A⁴ is a nitrogen atom-bearing group can be exemplified by

-   N-(2-dimethylaminoethyl)acrylamide, -   N-(2-diethylaminoethyl)acrylamide, -   N-(3-dimethylaminopropyl)acrylamide, -   N-(3-diethylaminopropyl)acrylamide, -   N-(4-dimethylaminobutyl)acrylamide, -   N-(4-diethylaminobutyl)acrylamide, -   N-(3-morpholinopropyl)acrylamide, and -   N-(3-cyanopropyl)acrylamide.

The methacrylamide compounds in which A⁴ is a nitrogen atom-bearing group can be exemplified by

-   N-(2-dimethylaminoethyl)methacrylamide, -   N-(2-diethylaminoethyl)methacrylamide, -   N-(3-dimethylaminopropyl)methacrylamide, -   N-(3-diethylaminopropyl)methacrylamide, -   N-(4-dimethylaminobutyl)methacrylamide, -   N-(4-diethylaminobutyl)methacrylamide, -   N-(3-morpholinopropyl)methacrylamide, and -   N-(3-cyanopropyl)methacrylamide.

The acrylamide compounds in which A⁴ is an oxygen atom-bearing group can be exemplified by

-   N-(3-methoxypropyl) acrylamide, -   N-(3-ethoxypropyl)acrylamide, -   N-(propoxymethyl)acrylamide, -   N-(butoxymethyl)acrylamide, -   N-glycidylacrylamide, and -   N-tetrahydrofurfurylacrylamide.

The methacrylamide compounds in which A⁴ is an oxygen atom-bearing group can be exemplified by

-   N-(3-methoxypropyl)methacrylamide, -   N-(3-ethoxypropyl)methacrylamide, -   N-(propoxymethyl)methacrylamide, -   N-(butoxymethyl)methacrylamide, -   N-glycidylmethacrylamide, and -   N-tetrahydrofurfurylmethacrylamide.

The acrylamide compounds in which A⁴ is a group bearing both nitrogen and oxygen atoms can be exemplified by N-(3-di(glycidyl)aminopropyl)acrylamide, and

-   N-(3-di(tetrahydrofurfuryl)aminopropyl)acrylamide.

The methacrylamide compounds in which A⁴ is a group bearing both nitrogen and oxygen atoms can be exemplified by N-(3-di(glycidyl)aminopropyl)methacrylamide, and

-   N-(3-di(tetrahydrofurfuryl)aminopropyl)methacrylamide.

The compounds represented by formula (IV) can also be exemplified by compounds in which A³ is an oxygen atom, such as acrylate compounds and methacrylate compounds.

The acrylate compounds in which A⁴ is a nitrogen atom-bearing group can be exemplified by

-   2-dimethylaminoethyl acrylate, -   2-diethylaminoethyl acrylate, -   3-dimethylaminopropyl acrylate, -   3-diethylaminopropyl acrylate, -   4-dimethylaminobutyl acrylate, and -   4-diethylaminobutyl acrylate.

The methacrylate compounds in which A⁴ is a nitrogen atom-bearing group can be exemplified by

-   2-dimethylaminoethyl methacrylate, -   2-diethylaminoethyl methacrylate, -   3-dimethylaminopropyl methacrylate, -   3-diethylaminopropyl methacrylate, -   4-dimethylaminobutyl methacrylate, and -   4-diethylaminobutyl methacrylate.

The acrylate compounds in which A⁴ is an oxygen atom-bearing group can be exemplified by

-   2-ethoxyethyl acrylate, -   2-propoxyethyl acrylate, -   2-butoxyethyl acrylate, -   3-methoxypropyl acrylate, -   3-ethoxypropyl acrylate, -   glycidyl acrylate, and -   tetrahydrofurfuryl acrylate.

The methacrylate compounds in which A⁴ is an oxygen atom-bearing group can be exemplified by

-   2-ethoxyethyl methacrylate, -   2-propoxyethyl methacrylate, -   2-butoxyethyl methacrylate, -   3-methoxypropyl methacrylate, -   3-ethoxypropyl methacrylate, -   glycidyl methacrylate, and -   tetrahydrofurfuryl methacrylate.

The acrylate compounds in which A⁴ is a group bearing both nitrogen and oxygen atoms can be exemplified by

-   3-di(glycidyl)aminopropyl acrylate, and -   3-di(tetrahydrofurfuryl)aminopropyl acrylate.

The methacrylate compounds in which A⁴ is a group bearing both nitrogen and oxygen atoms can be exemplified by 3-di(glycidyl)aminopropyl methacrylate, and

-   3-di(tetrahydrofurfuryl)aminopropyl methacrylate.

In view of enhancing the fuel economy, wet-grip performance, abrasion resistance, and processability in a balanced manner, the compound represented by formula (IV) is preferably a compound in which A⁴ is a group represented by formula (IVa), more preferably a compound in which A³ is an amino group and A⁴ is a group represented by formula (IVa), and still more preferably a compound in which A³ is a secondary amino group (—NH—) and A⁴ is a group represented by formula (IVa).

The compound in which A³ is a secondary amino group and A⁴ is a group represented by formula (IVa) is preferably an N-(3-dialkylaminopropyl)acrylamide or an N-(3-dialkylaminopropyl)methacrylamide, and more preferably

-   N-(3-dimethylaminopropyl)acrylamide, -   N-(3-diethylaminopropyl)acrylamide, -   N-(3-dimethylaminopropyl)methacrylamide, or -   N-(3-diethylaminopropyl)methacrylamide.

The following explains the silicon compound (modifying agent 4) containing a group represented by formula (V) below and/or a group represented by formula (VI) below.

Examples of groups containing the group represented by formula (V) include an amide group, a carboxylic acid ester group, a methacryloyl group, and an acryloyl group. Examples of groups containing the group represented by formula (VI) include oxydialkylene groups such as oxydimethylene and oxydiethylene groups; and alkylene oxide groups such as epoxy and tetrahydrofuranyl groups.

As used herein, the term “alkylene oxide group” denotes a monovalent group obtained by removing a hydrogen atom from the ring of a cyclic ether compound.

The silicon compound preferably contains a group represented by the following formula (VIII):

wherein R⁴¹, R⁴², and R⁴³ each independently represent a C₁₋₄ hydrocarbyl group or a C₁₋₄ hydrocarbyloxy group, and at least one of R⁴¹, R⁴², and R⁴³ is the hydrocarbyloxy group.

The hydrocarbyl groups encompassed by R⁴¹, R⁴², and R⁴³ in formula (VIII) can be exemplified by alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, and tert-butyl groups. The hydrocarbyloxy groups encompassed by R⁴¹, R⁴², and R⁴³ can be exemplified by alkoxy groups such as methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, sec-butoxy, and t-butoxy groups.

The hydrocarbyl group encompassed by R⁴¹, R⁴², and R⁴³ is preferably an alkyl group, more preferably a C₁₋₃ alkyl group, and still more preferably a methyl group or an ethyl group. The hydrocarbyloxy group encompassed by R⁴¹, R⁴², and R⁴³ is preferably an alkoxy group, more preferably a C₁₋₃ alkoxy group, and still more preferably a methoxy group or an ethoxy group.

In view of enhancing the fuel economy, wet-grip performance, abrasion resistance, and processability in a balanced manner, preferably at least two of R⁴¹, R⁴², and R⁴³ are hydrocarbyloxy groups, and more preferably the three of R⁴¹, R⁴², and R⁴³ are hydrocarbyloxy groups.

The silicon compounds containing a group represented by formula (V) and a group represented by formula (VIII) can be exemplified by silicon compounds containing a group represented by the following formula (Va):

wherein h represents an integer of 1 to 10; and R⁴⁴, R⁴⁵, and R⁴⁶ each independently represent a C₁₋₄ hydrocarbyl group or a C₁₋₄ hydrocarbyloxy group, and at least one of R⁴⁴, R⁴⁵, and R⁴⁶ is the hydrocarbyloxy group.

Here, h represents an integer of 1 to 10, and is preferably not less than 2 in view of enhancing the fuel economy, wet-grip performance, abrasion resistance, and processability in a balanced manner, whereas h is preferably not more than 4 in view of enhancing the economic efficiency of the production. Particularly preferably, h is 3.

Exemplary groups and preferred groups for R⁴⁴, R⁴⁵, and R⁴⁶ are the same as the exemplary groups and preferred groups mentioned above for R⁴¹, R⁴², and R⁴³ in formula (VIII).

The silicon compounds containing a group represented by formula (Va) can be exemplified by compounds represented by the following formula (Va-1) and compounds represented by the following formula (Va-2):

wherein i represents an integer of 1 to 10; R⁴⁷, R⁴⁸, and R⁴⁹ each independently represent a C₁₋₄ hydrocarbyl group or a C₁₋₄ hydrocarbyloxy group, and at least one of R⁴⁷, R⁴⁸, and R⁴⁹ is a hydrocarbyloxy group; and R⁵⁰ and R⁵¹ each independently represent a C₁₋₁₀ hydrocarbyl group, a C₁₋₁₀ substituted hydrocarbyl group, a C₁₋₁₀ hydrocarbyloxy group, or a C₁₋₁₉ substituted hydrocarbyloxy group, and R⁵⁰ and R⁵¹ may be bonded to each other;

wherein j, k, and l each independently represent an integer of 1 to 10; and R⁵² to R⁶⁰ each independently represent a C₁₋₄ hydrocarbyl group or a C₁₋₄ hydrocarbyloxy group, at least one of R⁵², R⁵³, and R⁵⁴ is a hydrocarbyloxy group, at least one of R⁵⁵, R⁵⁶, and R⁵⁷ is a hydrocarbyloxy group, and at least one of R⁵⁸, R⁵⁹, and R⁶⁰ is a hydrocarbyloxy group.

In formula (Va-1), i represents an integer of 1 to 10. Here, i is preferably not less than 2 in view of enhancing the fuel economy, wet-grip performance, abrasion resistance, and processability in a balanced manner, whereas i is preferably not more than 4 in view of enhancing the economic efficiency of the production. Particularly preferably, i is 3.

The hydrocarbyl groups encompassed by R⁴⁷, R⁴⁸, and R⁴⁹ in formula (Va-1) can be exemplified by alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, and tert-butyl groups. The hydrocarbyloxy groups encompassed by R⁴⁷, R⁴⁸, and R⁴⁹ can be exemplified by alkoxy croups such as methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, sec-butoxy, and t-butoxy groups.

The hydrocarbyl group encompassed by R⁴⁷, R⁴⁸, and R⁴⁹ is preferably an alkyl group, more preferably a C₁₋₃ alkyl group, and still more preferably a methyl group or an ethyl group. The hydrocarbyloxy group encompassed by R⁴⁷, R⁴⁸, and R⁴⁹ is preferably an alkoxy group, more preferably a C₁₋₃ alkoxy group, and still more preferably a methoxy group or an ethoxy group.

With regard to R⁴⁷, R⁴⁸, and R⁴⁹, in view of enhancing the fuel economy, wet-grip performance, abrasion resistance, and processability in a balanced manner, preferably at least two of R⁴⁷, R⁴⁸, and R⁴⁹ are hydrocarbyloxy groups, and more preferably the three of R⁴⁷, R⁴⁸, and R⁴⁹ are hydrocarbyloxy groups.

The hydrocarbyl groups encompassed by R⁵⁰ and R⁵¹ can be exemplified by alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, and tert-butyl groups.

The substituted hydrocarbyl groups encompassed by R⁵⁰ and R⁵¹ can be exemplified by substituted hydrocarbyl groups containing as a substituent at least one group selected from the group consisting of nitrogen atom-bearing groups, oxygen atom-bearing groups, and silicon atom-bearing groups. The groups containing a nitrogen atom-bearing group as a substituent can be exemplified by dialkylaminoalkyl groups such as dimethylaminoethyl and diethylaminoethyl groups. The groups containing an oxygen atom-bearing group as a substituent can be exemplified by alkoxyalkyl groups such as methoxymethyl, methoxyethyl, ethoxymethyl, and ethoxyethyl groups. The groups containing a silicon atom-bearing group as a substituent can be exemplified by trialkylsilylalkyl groups such as trimethylsilylmethyl and triethylsilylmethyl groups.

The hydrocarbyloxy groups encompassed by R⁵⁰ and R⁵¹ can be exemplified by alkoxy groups such as methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, sec-butoxy, and t-butoxy groups. The substituted hydrocarbyloxy groups encompassed by R⁵⁰ and R⁵¹ can be exemplified by alkoxyalkoxy groups such as methoxymethoxy, methoxyethoxy, ethoxymethoxy, and ethoxyethoxy groups.

The groups in which R⁵⁰ and R⁵¹ are bonded to each other can be exemplified by C₂₋₁₂ divalent groups optionally containing at least one atom selected from the group consisting of a nitrogen atom, an oxygen atom, and a silicon atom. Specific examples thereof include alkylene groups such as trimethylene, tetramethylene, pentamethylene, and hexamethylene groups; oxydialkylene groups such as oxydiethylene and oxydipropylene groups; and nitrogenous groups such as a group represented by —CH₂CH₂—NH—CH₂— and a group represented by —CH₂CH₂—N═CH—.

R⁵⁰ is preferably an alkyl group, more preferably a C₁₋₄ alkyl group, and still more preferably a methyl group or an ethyl group.

R⁵¹ is preferably an alkyl group, more preferably a C₁₋₄ alkyl group, and still more preferably a methyl group or an ethyl group.

In formula (Va-2), j, k, and l each independently represent an integer of 1 to 10, and are each independently preferably not less than 2 in view of enhancing the fuel economy, wet-grip performance, abrasion resistance, and processability in a balanced manner, whereas j, k, and l are each independently preferably not more than 4 in view of enhancing the economic efficiency of the production. Particularly preferably, j, k, and l are each independently 3.

The hydrocarbyl groups encompassed by R⁵² to R⁶⁰ in formula (Va-2) can be exemplified by alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, and tert-butyl groups. The hydrocarbyloxy groups encompassed by R⁵² to R⁶⁰ can be exemplified by alkoxy groups such as methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, sec-butoxy, and t-butoxy groups.

The hydrocarbyl group encompassed by R⁵² to R⁶⁰ is preferably an alkyl group, more preferably a alkyl group, and still more preferably a methyl group or an ethyl group. The hydrocarbyloxy group encompassed by R⁵² to R⁶⁰ is preferably an alkoxy group, more preferably a C₁₋₃ alkoxy group, and still more preferably a methoxy group or an ethoxy group.

With regard to R⁵², R⁵³, and R⁵⁴, in view of enhancing the fuel economy, wet-grip performance, abrasion resistance, and processability in a balanced manner, preferably at least two of R⁵², R⁵³, and R⁵⁴ are hydrocarbyloxy groups, and more preferably the three of R⁵², R⁵³, and R⁵⁴ are hydrocarbyloxy groups. With regard to R⁵⁵, R⁵⁶, and R⁵⁷, in view of enhancing the fuel economy, wet-grip performance, abrasion resistance, and processability in a balanced manner, preferably at least two of R⁵⁵, R⁵⁶, and R⁵⁷ are hydrocarbyloxy groups, and more preferably the three of R⁵⁵, R⁵⁶, and R⁵⁷ are hydrocarbyloxy groups. With regard to R⁵⁸, R⁵⁹, and R⁶⁰, in view of enhancing the fuel economy, wet-grip performance, abrasion resistance, and processability in a balanced manner, preferably at least two of R⁵⁸, R⁵⁹, and R⁶⁰ are hydrocarbyloxy groups, and more preferably the three of R⁵⁸, R⁵⁹, and R⁶⁰ are hydrocarbyloxy groups.

The compounds represented by formula (Va-1) can be exemplified by N-alkyl-N-trialkoxysilylalkyl-substituted carboxylic acid amides such as

-   N-alkyl-N-trialkoxysilylalkyl-acetamides, e.g., -   N-methyl-N-(trimethoxysilylmethyl)acetamide, -   N-methyl-N-(triethoxysilylmethyl)acetamide, -   N-methyl-N-(2-trimethoxysilylethyl)acetamide, -   N-methyl-N-(2-triethoxysilylethyl)acetamide, -   N-methyl-N-(3-trimethoxysilylpropyl)acetamide, and -   N-methyl-N-(3-triethoxysilylpropyl)acetamide; and -   N-alkyl-N-trialkoxysilylalkyl-propionamides, e.g., -   N-methyl-N-(trimethoxysilylmethyl)propionamide, -   N-methyl-N-(triethoxysilylmethyl)propionamide, -   N-methyl-N-(2-trimethoxysilylethyl)propionamide, -   N-methyl-N-(2-triethoxysilylethyl)propionamide, -   N-methyl-N-(3-trimethoxysilylpropyl)propionamide, and -   N-methyl-N-(3-triethoxysilylpropyl)propionamide.

The compound represented by formula (Va-1) is preferably an N-alkyl-N-trialkoxysilylalkyl-substituted carboxylic acid amide, more preferably an N-alkyl-N-trialkoxysilylalkyl-propionamide, and still more preferably N-methyl-N-(3-trimethoxysilylpropyl)-propionamide or N-methyl-N-(3-triethoxysilylpropyl)-propionamide.

The compounds represented by formula (Va-2) can be exemplified by 1,3,5-tris(trialkoxysilylalkyl)-isocyanurates such as

-   1,3,5-tris(trimethoxysilylmethyl)isocyanurate, -   1,3,5-tris(triethoxysilylmethyl)isocyanurate, -   1,3,5-tris(trimethoxysilylethyl)isocyanurate, -   1,3,5-tris(triethoxysilylethyl)isocyanurate, -   1,3,5-tris(3-trimethoxysilylpropyl)isocyanurate, and -   1,3,5-tris(3-triethoxysilylpropyl)isocyanurate.

The compound represented by formula (Va-2) is preferably 1,3,5-tris(3-trimethoxysilylpropyl)isocyanurate, or 1,3,5-tris(3-triethoxysilylpropyl)isocyanurate.

The silicon compounds containing a group represented by formula (VI) and a group represented by formula (VIII) can be exemplified by silicon compounds represented by the following formula (VIa):

wherein v represents an integer of 1 to 10; R⁶¹, R⁶², and R⁶³ each independently represent a C₁₋₄ hydrocarbyl group or a C₁₋₄ hydrocarbyloxy group, and at least one of R⁶¹, R⁶², and R⁶³ is a hydrocarbyloxy group; and R⁶⁴ represents a C₁₋₁₀ hydrocarbyl group or a C₁₋₁₀ substituted hydrocarbyl group.

In formula (VIa), v represents an integer of 1 to 10. Preferably, v is not less than 2 in view of enhancing the fuel economy, wet-grip performance, abrasion resistance, and processability in a balanced manner. Preferably, v is not more than 4 in view of enhancing the economic efficiency of the production. Particularly preferably, v is 3.

The hydrocarbyl groups encompassed by R⁶¹, R⁶², and R⁶³ in formula (VIa) can be exemplified by alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, and tert-butyl groups. The hydrocarbyloxy groups encompassed by R⁶¹, R⁶², and R⁶³ can be exemplified by alkoxy groups such as methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, sec-butoxy, and t-butoxy groups.

The hydrocarbyl group encompassed by R⁶¹, R⁶², and R⁶³ is preferably an alkyl group, more preferably a C₁₋₃ alkyl group, and still more preferably a methyl group or an ethyl group. The hydrocarbyloxy group encompassed by R⁶², and R⁶³ is preferably an alkoxy group, more preferably a C₁₋₃ alkoxy group, and still more preferably a methoxy group or an ethoxy group.

With regard to R⁶¹, R⁶², and R⁶³, in view of enhancing the fuel economy, wet-grip performance, abrasion resistance, and processability in a balanced manner, preferably at least two of R⁶¹, R⁶², and R⁶³ are hydrocarbyloxy groups, and more preferably the three of R⁶¹, R⁶², and R⁶³ are hydrocarbyloxy groups.

The hydrocarbyl groups encompassed by R⁶⁴ can be exemplified by alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, and tert-butyl groups.

The substituted hydrocarbyl groups encompassed by R⁶⁴ can be exemplified by substituted hydrocarbyl groups containing as a substituent at least one group selected from the group consisting of nitrogen atom-bearing groups, oxygen atom-bearing groups, and silicon atom-bearing groups. The groups containing a nitrogen atom-bearing group as a substituent can be exemplified by dialkylaminoalkyl groups such as dimethylaminoethyl and diethylaminoethyl groups. The groups containing an oxygen atom-bearing group as a substituent can be exemplified by alkoxyalkyl groups such as methoxymethyl, methoxyethyl, ethoxymethyl, and ethoxyethyl groups; and alkylene oxide alkyl groups such as glycidyl and tetrahydrofurfuryl groups. The groups containing a silicon atom-bearing group as a substituent can be exemplified by trialkylsilylalkyl groups such as a trimethylsilylmethyl group.

As used herein, the term “alkylene oxide alkyl group” denotes a group obtained by substituting at least one hydrogen atom of an alkyl group by an alkylene oxide group.

R⁶⁴ is preferably an alkylene oxide alkyl group, and more preferably a glycidyl group or a tetrahydrofurfuryl group.

The compounds represented by formula (VIa) in which R⁶⁴ is an alkyl group can be exemplified by

-   3-(alkoxy)propyltrialkoxysilanes such as -   3-(methoxy)propyltrimethoxysilane, -   3-(ethoxy)propyltrimethoxysilane, -   3-(n-propoxy)propyltrimethoxysilane, -   3-(isopropoxy)propyltrimethoxysilane, -   3-(n-butoxy)propyltrimethoxysilane, -   3-(sec-butoxy)propyltrimethoxysilane, and -   3-(t-butoxy)propyltrimethoxysilane.

The compounds represented by formula (VIa) in which R⁶⁴ is an alkylene oxide alkyl group can be exemplified by glycidoxyalkyltrialkoxysilanes such as

-   2-glycidoxyethyltrimethoxysilane, -   3-glycidoxypropyltrimethoxysilane, -   2-glycidoxyethyltriethoxysilane, and -   3-glycidoxypropyltriethoxysilane; and -   tetrahydrofurfuryloxyalkyltrialkoxysilanes such as -   2-tetrahydrofurfuryloxyethyltrimethoxysilane, -   3-tetrahydrofurfuryloxypropyltrimethoxysilane, -   2-tetrahydrofurfuryloxyethyltriethoxysilane, and -   3-tetrahydrofurfuryloxypropyltriethoxysilane.

The compounds represented by formula (VIa) in which R⁶⁴ is an alkoxyalkyl group can be exemplified by

-   3-(alkoxyalkoxy)propyltrialkoxysilanes such as -   3-(methoxymethoxy)propyltrimethoxysilane, -   3-(methoxyethoxy)propyltrimethoxysilane, -   3-(ethoxymethoxy)propyltrimethoxysilane, -   3-(ethoxyethoxy)propyltrimethoxysilane, -   3-(methoxymethoxy)propyltriethoxysilane, -   3-(methoxyethoxy)propyltriethoxysilane, -   3-(ethoxymethoxy)propyltriethoxysilane, and -   3-(ethoxyethoxy)propyltriethoxysilane.

The compound represented by formula (VIa) is preferably a compound in which R⁶⁴ is an alkylene oxide alkyl group, and more preferably

-   3-glycidoxypropyltrimethoxysilane, -   3-glycidoxypropyltriethoxysilane, -   3-tetrahydrofurfuryloxyprcpyltrimethoxysilane, or -   3-tetrahydrofurfuryloxypropyltriethoxysilane.

The silicon compounds containing a group represented by formula (V), a group represented by formula (VI), and a group represented by formula (VIII) can be exemplified by acryloxyalkyltrialkoxysilanes, and methacryloxyalkyltrialkoxysilanes.

The acryloxyalkyltrialkoxysilanes can be exemplified by 3-acryloxypropyltrialkoxysilanes such as 3-acryloxypropyltrimethoxysilane and 3-acryloxypropyltriethoxysilane.

The methacryloxyalkyltrialkoxysilanes can be exemplified by 3-methacryloxypropyltrialkoxysilanes such as 3-methacryloxypropyltrimethoxysilane, and 3-methacryloxypropyltriethoxysilane.

The silicon compounds containing a group represented by formula (V), a group represented by formula (VI), and a group represented by formula (VIII) can be further exemplified by trialkoxysilylalkylsuccinic anhydrides and trialkoxysilylalkylmaleic anhydrides.

The trialkoxysilylalkylsuccinic anhydrides can be exemplified by 3-trialkoxysilylpropylsuccinic anhydrides such as 3-trimethoxysilylpropylsuccinic anhydride and 3-triethoxysilylpropylsuccinic anhydride.

The trialkoxysilylalkylmaleic anhydrides can be exemplified by 3-trialkoxysilylpropylmaleic anhydrides such as 3-trimethoxysilylpropylmaleic anhydride and 3-triethoxysilylpropylmaleic anhydride.

The following explains the compound (modifying agent 5) containing a group represented by formula (VII) below.

In the formula, w represents an integer of 1 to 11, and A⁵ represents a nitrogen atom-bearing functional group.

Here, w represents an integer of 1 to 11, and is preferably not less than 1 in view of enhancing the fuel economy, wet-grip performance, abrasion resistance, and processability in a balanced manner, whereas w is preferably not more than 4 in view of enhancing the economic efficiency of the production. A⁵ represents a nitrogen atom-bearing functional group and examples include amino, isocyano, cyano, pyridyl, piperidyl, pyrazinyl, and morpholino groups.

The compounds containing a group represented by formula (VII) can be exemplified by compounds represented by the following formula (VII-1):

wherein z represents an integer of 0 to 10; R⁷¹ represents a C₁₋₅ hydrocarbyl group; R⁷², R⁷³, R⁷⁴ and R⁷⁵ each independently represent a hydrogen atom, a C₁₋₅ hydrocarbyl group, a C₁₋₅ substituted hydrocarbyl group, or a C₁₋₅ hydrocarbyloxy group, and when a plurality of R⁷²'s and a plurality of R⁷³'s are present, the plurality of R⁷²'s and the plurality of R⁷³'s may be the same as or different from one another; and R⁷⁶ and R⁷⁷ each independently represent a C₁₋₆ group optionally containing at least one atom selected from the group consisting of a nitrogen atom, an oxygen atom, and a silicon atom, R⁷⁶ and R⁷⁷ may be bonded to each other to form a cyclic structure together with the nitrogen atom, and R⁷⁶ and R⁷⁷ may form a single group bonded to the nitrogen via a double bond.

In formula (VII-1), z represents an integer of 0 to 10. In view of enhancing the economic efficiency, z is preferably not more than 3, and is more preferably 0.

R⁷¹ in formula (VII-1) represents a C₁₋₅ hydrocarbyl group. The hydrocarbyl groups encompassed by R⁷¹ can be exemplified by alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, and t-butyl groups.

The hydrocarbyl group encompassed by R⁷¹ is preferably an alkyl group, more preferably a C₁₋₄ alkyl group, and still more preferably a methyl group or an ethyl group.

R⁷² to R⁷⁵ in formula (VII-1) each independently represent a hydrogen atom, a C₁₋₅ hydrocarbyl group, a C₁₋₅ substituted hydrocarbyl group, or a C₁₋₅ hydrocarbyloxy group, and when a plurality of R⁷²'s and a plurality of R⁷³'s are present, the plurality of R⁷²'s and the plurality of R⁷³'s may be the same as or different from one another.

The hydrocarbyl groups encompassed by R⁷² to R⁷⁵ can be exemplified by alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, and t-butyl groups.

The substituted hydrocarbyl groups encompassed by R⁷² to R⁷⁵ can be exemplified by substituted hydrocarbyl groups containing as a substituent at least one group selected from the group consisting of nitrogen atom-bearing groups and oxygen atom-bearing groups. The groups containing a nitrogen atom-bearing group as a substituent can be exemplified by dialkylaminoalkyl groups such as dimethylaminoethyl and diethylaminoethyl groups. The groups containing an oxygen atom-bearing group as a substituent can be exemplified by alkoxyalkyl groups such as methoxymethyl, methoxyethyl, ethoxymethyl, and ethoxyethyl groups.

The hydrocarbyloxy groups encompassed by R⁷² to R⁷⁵ can be exemplified by alkoxy groups such as methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, sec-butoxy, and t-butoxy groups.

The hydrocarbyl group encompassed by R⁷² to R⁷⁵ is preferably an alkyl group, more preferably a C₁₋₄ alkyl group, and still more preferably a methyl group or an ethyl group.

The substituted hydrocarbyl group encompassed by R⁷² to R⁷⁵ is preferably an alkoxyalkyl group, more preferably a C₁₋₄ alkoxyalkyl group, and still more preferably a methoxymethyl group or an ethoxyethyl group.

The hydrocarbyloxy group encompassed by R⁷² to R⁷⁵ is preferably an alkoxy group, more preferably a C₁₋₃ alkoxy group, and still more preferably a methoxy group or an ethoxy group.

In view of economic efficiency and in view of enhancing the fuel economy, wet-grip performance, abrasion resistance, and processability in a balanced manner, preferably one of R⁷⁴ and R⁷⁵ is a hydrogen atom. More preferably, one of R⁷⁴ and R⁷⁵ is a hydrogen atom and the other is an alkyl group or an alkoxy group. Still more preferably, one of R⁷⁴ and R⁷⁵ is a hydrogen atom and the other is an alkoxy group, particularly preferably a methoxy group or an ethoxy group.

R⁷⁶ and R⁷⁷ in formula (VII-1) each independently represent a group optionally containing at least one atom selected from the group consisting of a nitrogen atom, an oxygen atom, and a silicon atom; R⁷⁶ and R⁷⁷ may be bonded to each other to form a cyclic structure together with the nitrogen atom; and R⁷⁶ and R⁷⁷ may form a single group bonded to the nitrogen via a double bond.

Examples of R⁷⁶ and R⁷⁷ in formula (VII-1) include C₁₋₆ hydrocarbyl groups, C₁₋₆ substituted hydrocarbyl groups, and substituted silyl groups.

The hydrocarbyl groups encompassed by R⁷⁶ and R⁷⁷ can be exemplified by alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, n-pentyl, neopentyl, isopentyl, and n-hexyl groups; cycloalkyl groups such as a cyclohexyl group; and a phenyl group.

The substituted hydrocarbyl groups encompassed by R⁷⁶ and R⁷⁷ can be exemplified by substituted hydrocarbyl groups containing as a substituent at least one group selected from the group consisting of nitrogen atom-bearing groups, oxygen atom-bearing groups, and silicon atom-bearing groups. The groups containing a nitrogen atom-bearing group as a substituent can be exemplified by dialkylaminoalkyl groups such as dimethylaminoethyl and diethylaminoethyl groups. The groups containing an oxygen atom-bearing group as a substituent can be exemplified by alkoxyalkyl groups such as methoxymethyl, methoxyethyl, ethoxymethyl, and ethoxyethyl groups; alkylene oxide groups such as epoxy and tetrahydrofuranyl groups; and alkylene oxide alkyl groups such as glycidyl and tetrahydrofurfuryl groups. The groups containing a silicon atom-bearing group as a substituent can be exemplified by trialkylsilylalkyl groups such as a trimethylsilylmethyl group.

As used herein, the term “alkylene oxide group” denotes a monovalent group obtained by removing a hydrogen atom from the ring of a cyclic ether compound. The term “alkylene oxide alkyl group” denotes a group obtained by substituting at least one hydrogen atom of an alkyl group by an alkylene oxide group.

The substituted silyl groups encompassed by R⁷⁶ and R⁷⁷ can be exemplified by trialkylsilyl groups such as trimethylsilyl, triethylsilyl, and t-butyldimethylsilyl groups; and trialkoxysilyl groups such as a trimethoxysilyl group.

The groups in which R⁷⁶ and R⁷⁷ are bonded to each other can be exemplified by C₂₋₁₂ divalent groups optionally containing at least one atom selected from the group consisting of a nitrogen atom, an oxygen atom, and a silicon atom. Specific examples thereof include alkylene groups such as trimethylene, tetramethylene, pentamethylene, and hexamethylene groups; oxydialkylene groups such as oxydiethylene and oxydipropylene groups; and nitrogenous groups such as a group represented by —CH₂CH₂—NH—CH₂— and a group represented by —CH₂CH₂—N═CH—.

The group in which R⁷⁶ and R⁷⁷ are bonded to each other is preferably a nitrogenous group, and more preferably a group represented by —CH₂CH₂—NH—CH₂— or a group represented by —CH₂CH₂—N═CH—.

Examples of the single group bonded to the nitrogen via a double bond, formed by R⁷⁶ and R⁷⁷, include C₂₋₁₂ divalent groups optionally containing at least one atom selected from the group Consisting of a nitrogen atom, an oxygen atom, and a silicon atom. Specific examples thereof include an ethylidene group, a 1-methylpropylidene group, a 1,3-dimethylbutylidene group, a 1-methylethylidene group, and a 4-N,N-dimethylaminobenzylidene group.

The hydrocarbyl group encompassed by R⁷⁶ and R⁷⁷ is preferably an alkyl group, more preferably a C₁₋₄ alkyl group, still more preferably a methyl group, an ethyl group, an n-propyl group, or an n-butyl group, and further preferably a methyl group or an ethyl group. The substituted hydrocarbyl group encompassed by R⁷⁶ and R⁷⁷ is preferably an alkoxyalkyl group, an alkylene oxide group, or an alkylene oxide alkyl group. The substituted silyl group encompassed by R⁷⁶ and R⁷⁷ is preferably a trialkylsilyl group or a trialkoxysilyl group, more preferably a trialkylsilyl group, and still more preferably a trimethylsilyl group or a triethylsilyl group.

Preferably, R⁷⁶ and R⁷⁷ are a nitrogenous group in which R⁷⁶ and R⁷⁷ are bonded to each other, or are each independently an alkyl group, an alkoxyalkyl group, or a substituted silyl group, more preferably a C₁₋₄ alkyl group, still more preferably a methyl group, an ethyl group, an n-propyl group, or an n-butyl group, and further preferably a methyl group or an ethyl group.

Examples of the amino group in which R⁷⁶ and R⁷⁷ are bonded to the nitrogen atom include acyclic amino groups and cyclic amino groups.

Examples of the acyclic amino groups include dialkylamino groups such as dimethylamino, diethylamino, di(n-propyl)amino, di(isopropyl)amino, di(n-butyl)amino, di(sec-butyl)amino, di(tert-butyl)amino, di(neopentyl)amino, and ethylmethylamino groups; di(alkoxyalkyl)amino groups such as di(methoxymethyl)amino, di(methoxyethyl)amino, di(ethoxymethyl)amino, and di(ethoxyethyl)amino groups; and di(trialkylsilyl)amino groups such as di(trimethylsilyl)amino and di(t-butyldimethylsilyl)amino groups. Other examples include di(alkylene oxide)amino groups such as di(epoxy)amino and di(tetrahydrofuranyl)amino groups; and di(alkylene oxide alkyl)amino groups such as di(glycidyl)amino and di(tetrahydrofurfuryl)amino groups. Additional examples include ethylideneamino, 1-methylpropylideneamino, 1,3-dimethylbutylideneamino, 1-methylethylideneamino, and 4-N,N-dimethylaminobenzylideneamino groups.

The cyclic amino groups can be exemplified by 1-polymethyleneimino groups such as 1-pyrrolidinyl, 1-piperidino, 1-hexamethyleneimino, 1-heptamethyleneimino, 1-octamethyleneimino, 1-decamethyleneimino, and 1-dodecamethyleneimino groups. The cyclic amino groups can also be exemplified by 1-imidazolyl, 4,5-dihydro-1-imidazolyl, 1-imidazolidinyl, 1-piperazinyl, and morpholino groups.

In view of fuel economy, wet-grip performance, abrasion resistance, processability, and long-term stability and easy availability of the compound, the amino group in which R⁷⁶ and R⁷⁷ are bonded to the nitrogen atom is preferably an acyclic amino group, more preferably a dialkylamino group, and still more preferably a dimethylamino group or a diethylamino group.

The compounds represented by formula (VII-1) can be exemplified by N,N-dialkyl-substituted carboxylic acid amide dialkyl acetal compounds.

The N,N-dialkyl-substituted carboxylic acid amide dialkyl acetal compounds can be exemplified by

-   N,N-dialkylformamide dialkyl acetals such as -   N,N-dimethylformamide dimethyl acetal, -   N,N-diethylformamide dimethyl acetal, -   N,N-di(n-propyl)formamide dimethyl acetal, -   N,N-dimethylformamide diethyl acetal, -   N,N-diethylformamide diethyl acetal, -   N,N-di(n-propyl)formamide diethyl acetal, -   N,N-dimethylformamide ethyl methyl acetal, -   N,N-diethylformamide ethyl methyl acetal, and -   N,N-di(n-propyl)formamide ethyl methyl acetal; -   N,N-dialkylacetamide dialkyl acetals such as -   N,N-dimethylacetamide dimethyl acetal, -   N,N-diethylacetamide dimethyl acetal, -   N,N-di(n-propyl)acetamide dimethyl acetal, -   N,N-dimethylacetamide diethyl acetal, -   N,N-diethylacetamide diethyl acetal, -   N,N-di(n-propyl)acetamide diethyl acetal, -   N,N-dimethylacetamide ethyl methyl acetal, -   N,N-diethylacetamide ethyl methyl acetal, and -   N,N-di(n-propyl)acetamide ethyl methyl acetal; and -   N,N-dialkylpropionamide dialkyl acetals such as -   N,N-dimethylpropionamide dimethyl acetal, -   N,N-diethylpropionamide dimethyl acetal, -   N,N-di(n-propyl)propionamide dimethyl acetal, -   N,N-dimethylpropionamide diethyl acetal, -   N,N-diethylpropionamide diethyl acetal, -   N,N-di(n-propyl)propionamide diethyl acetal, -   N,N-dimethylpropionamide ethyl methyl acetal. -   N,N-diethylpropionamide ethyl methyl acetal, and -   N,N-di(n-propyl)propionamide ethyl methyl acetal.

In view of enhancing the fuel economy, wet-grip performance, abrasion resistance, and processability in a balanced manner, N,N-dialkylformamide dialkyl acetals are preferred among the preceding and N,N-dimethylformamide dimethyl acetal, N,N-diethylformamide dimethyl acetal, N,N-dimethylformamide diethyl acetal, and N,N-diethylformamide diethyl acetal are more preferred.

In addition to the conjugated diene-based constituent unit (conjugated diene unit), the conjugated diene polymer may also contain a constituent unit based on another monomer. Such other monomers include aromatic vinyls, vinyl nitriles, unsaturated carboxylic acid esters, and the like. The aromatic vinyls can be exemplified by styrene, α-methylstyrene, vinyltoluene, vinylnaphthalene, divinylbenzene, trivinylbenzene, and divinylnaphthalene. The vinyl nitriles can be exemplified by acrylonitrile. The unsaturated carboxylic acid esters can be exemplified by methyl acrylate, ethyl acrylate, methyl methacrylate, and ethyl methacrylate. Aromatic vinyls are preferred among the preceding, and styrene is more preferred.

The conjugated diene polymer preferably contains an aromatic vinyl-based constituent unit (aromatic vinyl unit) in consideration of abrasion resistance. In this case, the aromatic vinyl unit content, based on a total of 100% by mass of the conjugated diene unit and the aromatic vinyl unit, is preferably at least 10% by mass (the conjugated diene unit content is not more than 90% by mass), and more preferably at least 15% by mass (the conjugated diene unit content is not more than 85% by mass). In view of fuel economy, the aromatic vinyl unit content is preferably not more than 50% by mass (the conjugated diene unit content is at least 50% by mass), and more preferably not more than 45% by mass (the conjugated diene unit content is at least 55% by mass).

In view of fuel economy, the conjugated diene polymer preferably has a vinyl bond content of not more than 80 mol %, more preferably not more than 70 mol %, per 100 mol % of the conjugated diene unit. In view of wet-grip performance, the vinyl bond content is preferably at least 10 mol %, more preferably at least 15 mol %, still more preferably at least 20 mol %, and particularly preferably at least 40 mol %. The vinyl bond content can be determined by infrared spectroscopic analysis from the intensity of the absorption in the vicinity of 910 cm⁻¹, which is an absorption peak for a vinyl group.

The molecular weight distribution of the conjugated diene polymer, in view of fuel economy, is preferably 1 to 5, and more preferably 1 to 2. The molecular weight distribution can be determined by measuring the number-average molecular weight (Mn) and the weight-average molecular weight (Mw) by gel permeation chromatography (GPC) and dividing Mw by Mn.

The conjugated diene polymer may suitably be produced by a method including the following Step A and Step B.

(Step A): A step of polymerizing monomers including a conjugated diene and a vinyl compound represented by formula (IX) below in the presence of an alkali metal catalyst in a hydrocarbon solvent to obtain a polymer that contains a constituent unit based on the conjugated diene and a constituent unit based on the vinyl compound represented by the formula (IX) and has an alkali metal derived from the catalyst at least one polymer chain terminal:

wherein X⁴, X⁵, and X⁶ each independently represent a group represented by formula (IXa) below, a hydrocarbyl group, or a substituted hydrocarbyl group, and at least one of X⁴, X⁵, and X⁶ is a group represented by the following formula (IXa):

wherein R⁸¹ and R⁸² each independently represent a C₁₋₆ hydrocarbyl group, a C₁₋₆ substituted hydrocarbyl group, a silyl group, or a substituted silyl group, and R⁸¹ and R⁸² may be bonded to each other to form a cyclic structure together with the nitrogen atom.

(Step B): A step of reacting the polymer obtained in Step A with at least one of the modifying agents 1 to 5.

The alkali metal catalysts that can be used in (Step A) can be exemplified by alkali metals, organoalkali metal compounds, alkali metal/polar compound complexes, and alkali metal-containing oligomers. Examples of the alkali metals include lithium, sodium, potassium, rubidium, and cesium. Examples of the organoalkali metal compounds include ethyllithium, n-propyllithium, iso-propyllithium, n-butyllithium, sec-butyllithium, t-octyllithium, n-decyllithium, phenyllithium, 2-naphthyllithium, 2-butylphenyllithium, 4-phenylbutyllithium, cyclohexyllithium, 4-cyclopentyllithium, dimethylaminopropyllithium, diethylaminopropyllithium, t-butyldimethylsilyloxypropyllithium, N-morpholinopropyllithium, lithium hexamethyleneimide, lithium pyrrolidide, lithium piperidide, lithium heptamethyleneimide, lithium dodecamethyleneimide, 1,4-dilithio-2-butene, sodium naphthalenide, sodium biphenylide, and potassium naphthalenide. Examples of the alkali metal/polar compound complexes include potassium-tetrahydrofuran complexes and potassium-diethoxyethane complexes. Examples of the alkali metal-containing oligomers include sodium salts of α-methylstyrene tetramer. Organolithium compounds and organosodium compounds are preferred among the preceding, and C₂₋₂₀ organolithium or organosodium compounds are more preferred.

The hydrocarbon solvent used in (Step A) is a solvent that does not deactivate the organoalkali metal compound catalyst, and examples thereof include aliphatic hydrocarbons, aromatic hydrocarbons, and alicyclic hydrocarbons. The aliphatic hydrocarbons can be exemplified by propane, n-butane, iso-butane, n-pentane, iso-pentane, n-hexane, propene, 1-butene, iso-butene, trans-2-butene, cis-2-butene, 1-pentene, 2-pentene, 1-hexene, and 2-hexene. The aromatic hydrocarbons can be exemplified by benzene, toluene, xylene, and ethylbenzene. The alicyclic hydrocarbons can be exemplified by cyclopentane and cyclohexane. These may be used alone or two or more may be used in combination. C₂₋₁₂ hydrocarbons are preferred among the preceding.

In (Step A), monomers including a conjugated diene and a vinyl compound represented by formula (IX) are polymerized to produce a conjugated diene polymer having an alkali metal derived from the above-described alkali metal catalyst at a polymer chain terminal. The conjugated dienes can be exemplified by 1,3-butadiene, isoprene, 1,3-pentadiene, 2,3-dimethyl-1,3-butadiene, and 1,3-hexadiene. These may be used alone or two or more may be used in combination. In view of ease of availability, 1,3-butadiene and isoprene are preferred among the preceding.

X⁴, X⁵ and X⁶ in formula (IX) each independently represent a group represented by formula (IXa), a hydrocarbyl group, or a substituted hydrocarbyl group, and at least one of X⁴, X⁵, and X⁶ is a group represented by formula (IXa).

R⁸¹ and R⁸² in formula (IXa) each independently represent a C₁₋₆ hydrocarbyl group, a C₁₋₆ substituted hydrocarbyl group, a silyl group, or a substituted silyl group, and R⁸¹ and R⁸² may be bonded to each other to form a cyclic structure together with the nitrogen atom.

The C₁₋₆ hydrocarbyl groups encompassed by R⁸¹ and R⁸² can be exemplified by alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, n-pentyl, neopentyl, isopentyl, and n-hexyl groups; cycloalkyl groups such as a cyclohexyl group; and a phenyl group.

The C₁₋₆ substituted hydrocarbyl groups encompassed by R⁸¹ and R⁸² can be exemplified by substituted hydrocarbyl groups containing as a substituent at least one group selected from the group consisting of nitrogen atom-bearing groups, oxygen atom-bearing groups, and silicon atom-bearing groups. The groups containing a nitrogen atom-bearing group as a substituent can be exemplified by dialkylaminoalkyl groups such as dimethylaminoethyl and diethylaminoethyl groups. The groups containing an oxygen atom-bearing group as a substituent can be exemplified by alkoxyalkyl groups such as methoxymethyl, methoxyethyl, ethoxymethyl, and ethoxyethyl groups. The groups containing a silicon atom-bearing group as a substituent can be exemplified by trialkylsilylalkyl groups such as a trimethylsilylmethyl group.

The substituted silyl groups encompassed by R⁸¹ and R⁸² can be exemplified by trialkylsilyl groups such as trimethylsilyl, triethylsilyl, and t-butyldimethylsilyl groups.

The groups in which R⁸¹ and R⁸² are bonded to each other can be exemplified by C₁₋₁₂ divalent groups optionally containing at least one atom selected from the group consisting of a nitrogen atom, an oxygen atom, and a silicon atom. Specific examples thereof include alkylene groups such as trimethylene, tetramethylene, pentamethylene, and hexamethylene groups; oxydialkylene groups such as oxydiethylene and oxydipropylene groups; and nitrogenous groups such as a group represented by —CH₂CH₂—NH—CH₂— and a group represented by —CH₂CH₂—N═CH—.

The group in which R⁸¹ and R⁸² are bonded to each other is preferably a nitrogenous group, and more preferably a group represented by —CH₂CH₂—NH—CH₂— or a group represented by —CH₂CH₂—N═CH—.

The hydrocarbyl group encompassed by R⁸¹ and R⁸² is preferably an alkyl group, more preferably a C₁₋₄ alkyl group, still more preferably a methyl group, an ethyl group, an n-propyl group, or an n-butyl group, and particularly preferably an ethyl group or an n-butyl group. The substituted hydrocarbyl group encompassed by R⁸¹ and R⁸² is preferably an alkoxyalkyl group, and more preferably a C₁₋₄ alkoxyalkyl group. The substituted silyl group encompassed by R⁸¹ and R⁸² is preferably a trialkylsilyl group, and more preferably a trimethylsilyl group.

Preferably, R⁸¹ and R⁸² are a nitrogenous group in which R⁸¹ and R⁸² are bonded to each other, or are each independently an alkyl group, an alkoxyalkyl group, or a substituted silyl group, more preferably an alkyl group, still more preferably a C₁₋₄ alkyl group, and further preferably a methyl group, an ethyl group, an n-propyl group, or an n-butyl group.

Examples of the group represented by formula (IXa) include acyclic amino groups and cyclic amino groups.

The acyclic amino groups can be exemplified by dialkylamino groups such as dimethylamino, diethylamino, di(n-propyl)amino, di(isopropyl)amino, di(n-butyl)amino, di(sec-butyl)amino, di(tert-butyl)amino, di(neopentyl)amino, and ethylmethylamino groups; di(alkoxyalkyl)amino groups such as di(methoxymethyl)amino, di(methoxyethyl)amino, di(ethoxymethyl)amino, and di(ethoxyethyl)amino groups; and di(trialkylsilyl)amino groups such as di(trimethylsilyl)amino and di(t-butyldimethylsilyl)amino groups.

The cyclic amino groups can be exemplified by 1-polymethyleneimino groups such as 1-pyrrolidinyl, 1-piperidino, 1-hexamethyleneimino, 1-heptamethyleneimino, 1-octamethyleneimino, 1-decamethyleneimino, and 1-dodecamethyleneimino groups. The cyclic amino groups can also be exemplified by 1-imidazolyl, 4,5-dihydro-1-imidazolyl, 1-imidazolidinyl, 1-piperazinyl, and morpholino groups.

In view of economic efficiency and ease of availability, the group represented by formula (IXa) is preferably an acyclic amino group, more preferably a dialkylamino group, still more preferably a dialkylamino group which contains a C₁₋₄ alkyl group as a substituent, and further preferably a dimethylamino group, a diethylamino group, a di(n-propyl)amino group, or a di(n-butyl)amino group.

The hydrocarbyl groups encompassed by X⁴, X⁵, and X⁶ in formula (IX) can be exemplified by alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, and tert-butyl groups. The substituted hydrocarbyl groups can be exemplified by alkoxyalkyl groups such as methoxymethyl, ethoxymethyl, methoxyethyl, and ethoxyethyl groups.

The hydrocarbyl group encompassed by X⁴, X⁵, and X⁶ is preferably an alkyl group, more preferably a C₁₋₄ alkyl group, and still more preferably a methyl group or an ethyl group. The substituted hydrocarbyl group encompassed by X⁴, X⁵, and X⁶ is preferably an alkoxyalkyl group, and more preferably a C₁₋₄ alkoxyalkyl group.

The hydrocarbyl group or substituted hydrocarbyl group encompassed by X⁴, X⁵, and X⁶ is preferably an alkyl group or an alkoxyalkyl group, more preferably a C₁₋₄ alkyl group or a C₁₋₄ alkoxyalkyl group, still more preferably a C₁₋₄ alkyl group, and further preferably a methyl group or an ethyl group.

At least one of X⁴, X⁵, and X⁶ in formula (IX) is a group represented by formula (IXa). Preferably at least two of X⁴, X⁵, and X⁶ are groups represented by formula (IXa). More preferably two of X⁴, X⁵, and X⁶ are groups represented by formula (IXa).

Examples of the vinyl compound represented by formula (IX) used in (Step A) include compounds in which one of X⁴, X⁵, and X⁶ is an acyclic amino group represented by formula (IXa) and the other two are, independently, a hydrocarbyl group or a substituted hydrocarbyl group, e.g., (dialkylamino)dialkylvinylsilanes, {di(trialkylsilyl)amino}dialkylvinylsilanes, and (dialkylamino)dialkoxyalkylvinylsilanes.

The (dialkylamino)dialkylvinylsilanes can be exemplified by

-   (dimethylamino)dimethylvinylsilane, -   (ethylmethylamino)dimethylvinylsilane, -   (diethylamino)dimethylvinylsilane, -   (ethyl-n-propylamino)dimethylvinylsilane, -   (ethylisopropylamino)dimethylvinylsilane, -   (di(n-propyl)amino)dimethylvinylsilane, -   (diisopropylamino)dimethylvinylsilane, -   (n-butyl-n-propylamino)dimethylvinylsilane, -   (di(n-butyl)amino)dimethylvinylsilane, -   (dimethylamino)diethylvinylsilane, -   (ethylmethylamino)diethylvinylsilane, -   (diethylamino)diethylvinylsilane, -   (ethyl-n-propylamino) diethylvinylsilane, -   (ethylisopropylamino)diethylvinylsilane, -   (di(n-propyl)amino)diethylvinylsilane, -   (diisopropylamino)diethylvinylsilane, -   (n-butyl-n-propylamino) diethylvinylsilane, -   (di(n-butyl)amino)diethylvinylsilane, -   (dimethylamino)dipropylvinylsilane, -   (ethylmethylamino)dipropylvinylsilane, -   (diethylamino)dipropylvinylsilane, -   (ethyl-n-propylamino)dipropylvinylsilane, -   (ethylisopropylamino)dipropylvinylsilane, -   (di(n-propyl)amino)dipropylvinylsilane, -   (diisopropylamino)dipropylvinylsilane, -   (n-butyl-n-propylamino)dipropylvinylsilane, -   (di(n-butyl)amino)dipropylvinylsilane, -   (dimethylamino)dibutylvinylsilane, -   (ethylmethylamino)dibutylvinylsilane, -   (diethylamino)dibutylvinylsilane, -   (ethyl-n-propylamino)dibutylvinylsilane, -   (ethylisopropylamino)dibutylvinylsilane, -   (di(n-propyl)amino)dibutylvinylsilane, -   (diisopropylamino)dibutylvinylsilane, -   (n-butyl-n-propylamino)dibutylvinylsilane, and -   (di(n-butyl)amino)dibutylvinylsilane.

The {di(trialkylsilyl)amino}dialkylvinylsilanes can be exemplified by

-   {di(trimethylsilyl)amino}dimethylvinylsilane, -   {di(t-butyldimethylsilyl)amino}dimethylvinylsilane, -   {di(trimethylsilyl)amino}diethylvinylsilane, and -   {di(t-Butyldimethylsilyl)amino}diethylvinylsilane.

The (dialkylamino)dialkoxyalkylvinylsilanes can be exemplified by

-   (dimethylamino)dimethoxymethylvinylsilane, -   (dimethylamino)dimethoxyethylvinylsilane, -   (dimethylamino)diethoxymethylvinylsilane, -   (dimethylamino)diethoxyethylvinylsilane, -   (diethylamino)dimethoxymethylvinylsilane, -   (diethylamino)dimethoxyethylvinylsilane, -   (diethylamino)diethoxymethylvinylsilane, and -   (diethylamino)diethoxyethylvinylsilane.

Examples of compounds in which two of X⁴, X⁵, and X⁶ are acyclic amino groups represented by formula (IXa) and the other one is a hydrocarbyl group or a substituted hydrocarbyl group include bis(dialkylamino)-alkylvinylsilanes, bis{di(trialkylsilyl)amino}-alkylvinylsilanes, and bis(dialkylamino)-alkoxyalkylvinylsilanes.

The bis(dialkylamino)alkylvinylsilanes can be exemplified by bis(dimethylamino)methylvinylsilane,

-   bis(ethylmethylamino)methylvinylsilane, -   bis(diethylamino)methylvinylsilane, -   bis(ethyl-n-propylamino)methylvinylsilane, -   bis(ethylisopropylamino)methylvinylsilane, -   bis(di(n-propyl)amino)methylvinylsilane, -   bis(diisopropylamino)methylvinylsilane, -   bis(n-butyl-n-propylamino)methylvinylsilane, -   bis(di(n-butyl)amino)methylvinylsilane, -   bis(dimethylamino)ethylvinylsilane, -   bis(ethylmethylamino)ethylvinylsilane, -   bis(diethylamino)ethylvinylsilane, -   bis(ethyl-n-propylamino)ethylvinylsilane, -   bis(ethylisopropylamino)ethylvinylsilane, -   bis(di(n-propyl)amino)ethylvinylsilane, -   bis(diisopropylamino)ethylvinylsilane, -   bis(n-butyl-n-propylamino)ethylvinylsilane, -   bis(di(n-butyl)amino)ethylvinylsilane, -   bis(dimethylamino)propylvinylsilane, -   bis(ethylmethylamino)propylvinylsilane, -   bis(diethylamino)propylvinylsilane, -   bis(ethyl-n-propylamino)propylvinylsilane, -   bis(ethylisopropylamino)propylvinylsilane, -   bis(di(n-propyl)amino)propylvinylsilane, -   bis(diisopropylamino)propylvinylsilane, -   bis(n-butyl-n-propylamino)propylvinylsilane, -   bis(di(n-butyl)amino)propylvinylsilane, -   bis(dimethylamino)butylvinylsilane, -   bis(ethylmethylamino)butylvinylsilane, -   bis(diethylamino)butylvinylsilane, -   bis(ethyl-n-propylamino)butylvinylsilane, -   bis(ethylisopropylamino)butylvinylsilane, -   bis(di(n-propyl)amino)butylvinylsilane, -   bis(diisopropylamino)butylvinylsilane, -   bis(n-butyl-n-propylamino)butylvinylsilane, and -   bis(di(n-butyl)amino)butylvinylsilane.

The bis{di(trialkylsilyl)amino}alkylvinylsilanes can be exemplified by

-   bis{di(trimethylsilyl)amino}methylvinylsilane, -   bis{di(t-butyldimethylsilyl)amino}methylvinylsilane, -   bis{di(trimethylsilyl)amino}ethylvinylsilane, and -   bis{di(t-butyldimethylsilyl)amino}ethylvinylsilane.

The bis(dialkylamino)alkoxyalkylvinylsilanes can be exemplified by

-   bis(dimethylamino)methoxymethylvinylsilane, -   bis(dimethylamino)methoxyethylvinylsilane, -   bis(dimethylamino)ethoxymethylvinylsilane, -   bis(dimethylamino)ethoxyethylvinylsilane, -   bis(diethylamino)methoxymethylvinylsilane, -   bis(diethylamino)methoxyethylvinylsilane, -   bis(diethylamino)ethoxymethylvinylsilane, and -   bis(diethylamino)ethoxyethylvinylsilane.

Examples of compounds in which the three of X⁴, X⁵, and X⁶ are acyclic amino groups represented by formula (IXa) include tri(dialkylamino)vinylsilanes. Specific examples thereof include:

-   tri(dimethylamino)vinylsilane, -   tri(ethylmethylamino)vinylsilane, -   tri(diethylamino)vinylsilane, -   tri(ethylpropylamino)vinylsilane, -   tri(dipropylamino)vinylsilane, and -   tri(butylpropylamino)vinylsilane.

Examples of compounds in which two of X⁴, X⁵, and X⁶ are cyclic amino groups represented by formula (IXa) and the other one is a hydrocarbyl group or a substituted hydrocarbyl group include:

-   bis(morpholino)methylvinylsilane, -   bis(piperidino)methylvinylsilane, -   bis(4,5-dihydroimidazolyl)methylvinylsilane, and -   bis(hexamethyleneimino)methylvinylsilane.

The vinyl compound represented by formula (IX) in which two of X⁴, X⁵, and X⁶ are groups represented by formula (IXa) is preferably a vinyl compound in which two of X⁴, X⁵, and X⁶ are acyclic amino groups. In view of fuel economy, wet-grip performance, abrasion resistance, and processability, the vinyl compound is more preferably a bis(dialkylamino)alkylvinylsilane, and still more preferably bis(dimethylamino)methylvinylsilane, bis(diethylamino)methylvinylsilane, bis(di(n-propyl)amino)methylvinylsilane, or bis(di(n-butyl)amino)methylvinylsilane. Among the preceding, bis(diethylamino)methylvinylsilane and bis(di(n-butyl)amino)methylvinylsilane are preferred in terms of easy availability of the compound.

In (Step A), polymerization may be carried out by using the conjugated diene and the vinyl compound represented by formula (IX) in combination with another monomer. Such other monomers include aromatic vinyls, vinyl nitriles, unsaturated carboxylic acid esters, and the like. The aromatic vinyls can be exemplified by styrene, α-methylstyrene, vinyltoluene, vinylnaphthalene, divinylbenzene, trivinylbenzene, and divinylnaphthalene. The vinyl nitriles can be exemplified by acrylonitrile. The unsaturated carboxylic acid esters can be exemplified by methyl acrylate, ethyl acrylate, methyl methacrylate, and ethyl methacrylate. Aromatic vinyls are preferred among the preceding, and styrene is more preferred.

In (Step A), polymerization may be carried out in the presence of an agent that adjusts the vinyl bond content of the conjugated diene unit, an agent that adjusts the distribution of the conjugated diene unit and constituent unit(s) based on monomer(s) other than the conjugated diene in the conjugated diene polymer chain, or the like (these agents are collectively referred to below as “regulators”). Examples of these agents include ether compounds, tertiary amines, and phosphine compounds. The ether compounds can be exemplified by cyclic ethers such as tetrahydrofuran, tetrahydropyran, and 1,4-dioxane; aliphatic monoethers such as diethyl ether and dibutyl ether; aliphatic diethers such as ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dibutyl ether, diethylene glycol diethyl ether, and diethylene glycol dibutyl ether; and aromatic ethers such as diphenyl ether and anisole. The tertiary amines can be exemplified by triethylamine, tripropylamine, tributylamine, N,N,N′,N′-tetramethylethylenediamine, N,N-diethylaniline, pyridine, and quinoline. The phosphine compounds can be exemplified by trimethylphosphine, triethylphosphine, and triphenylphosphine. These may be used alone or two or more may be used in combination.

The polymerization temperature in (Step A) is typically 25 to 100° C., preferably 35 to 90° C., and more preferably 50 to 80° C. The polymerization time is typically 10 minutes to 5 hours.

In (Step B), the amount of the modifying agent(s) 1 to 5 to be contacted with the polymer prepared in Step A is typically 0.1 to 3 moles, preferably 0.5 to 2 moles, more preferably 0.7 to 1.5 moles, and further preferably 1 to 1.5 moles, per mole of the alkali metal derived from the organoalkali metal catalyst.

In (Step B), the temperature for the contact between the polymer prepared in Step A and at least one of the modifying agents 1 to 5 is typically 25 to 100° C., preferably 35 to 90° C., and more preferably 50 to 80° C. The contact time is typically 60 seconds to 5 hours, preferably 5 minutes to 1 hour, and more preferably 15 minutes to 1 hour.

In the method for producing the conjugated diene polymer, a coupling agent may be added to the hydrocarbon solution of the conjugated diene polymer as necessary, from the initiation of polymerization of monomers in the presence of the alkali metal catalyst to the termination of polymerization. The coupling agent may be a compound represented by the following formula (X): R⁹¹ _(a)ML_(4-a)  (X) wherein R⁹¹ represents an alkyl group, an alkenyl group, a cycloalkenyl group, or an aromatic residue; M represents a silicon atom or a tin atom; L represents a halogen atom or a hydrocarbyloxy group; and a represents an integer of 0 to 2.

The term “aromatic residue” denotes a monovalent group obtained by removing hydrogen bonded to the aromatic ring of an aromatic hydrocarbon.

The coupling agents represented by formula (X) can be exemplified by silicon tetrachloride, methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, tin tetrachloride, methyltrichlorotin, dimethyldichlorotin, trimethylchlorotin, tetramethoxysilane, methyltrimethoxysilane, dimethoxydimethylsilane, methyltriethoxysilane, ethyltrimethoxysilane, dimethoxydiethylsilane, diethoxydimethylsilane, tetraethoxysilane, ethyltriethoxysilane, and diethoxydiethylsilane.

In view of the processability of the conjugated diene polymer, the amount of the coupling agent is preferably not less than 0.03 moles, and more preferably not less than 0.05 moles, per mole of the alkali metal derived from the alkali metal catalyst. In view of fuel economy, the amount is preferably not more than 0.4 moles, and more preferably not more than 0.3 moles.

The conjugated diene polymer can be recovered from the hydrocarbon solution of the conjugated diene polymer by a known recovery method, for example, by (1) addition of a coagulant to the hydrocarbon solution of the conjugated diene polymer or (2) addition of steam to the hydrocarbon solution of the conjugated diene polymer. The recovered conjugated diene polymer may be dried using a known drier, for example, a band drier or an extrusion drier.

In the method for producing the conjugated diene polymer, a treatment in which the group represented by formula (Ia) in the polymer is replaced by a hydroxy group is preferably carried out by, for example, hydrolysis. This treatment may be carried out on the polymer alone or on a below-mentioned composition including the polymer. Examples of the hydrolysis method include known hydrolysis methods, e.g., methods using steam stripping. The treatment can convert at least one of X¹, X², and X³ in formula (I) into hydroxy group(s) and can thereby enhance the fuel economy, wet-grip performance, abrasion resistance, and processability in a more balanced manner.

The conjugated diene polymer can be used in the rubber component of the rubber composition of the present invention, and is preferably used in combination with other rubber materials, additives and the like.

Examples of other rubber materials include commonly used diene rubbers such as styrene-butadiene copolymer rubber (SBR), polybutadiene rubber (BR), butadiene-isoprene copolymer rubber, and butyl rubber. Moreover, natural rubber (NR), ethylene-propylene copolymers, ethylene-octene copolymers and the like may also be mentioned. Two or more kinds of these rubber materials may be used in combination. In particular, in view of enhancing the fuel economy, wet-grip performance, abrasion resistance, and processability in a balanced manner, NR and/or BR are preferably used, and both of NR and BR are more preferably used.

The conjugated diene polymer content, based on 100% by mass of the rubber component, is not less than 5% by mass, preferably not less than 10% by mass, more preferably not less than 30% by mass, and still more preferably not less than 50% by mass. The conjugated diene polymer content of less than 5% by mass tends to result in less improvement in fuel economy. The conjugated diene polymer content is preferably not more than 90% by mass, more preferably not more than 85% by mass, still more preferably not more than 80% by mass, and particularly preferably not more than 70% by mass. The conjugated diene polymer content in excess of 90% by mass tends to result in a decline in abrasion resistance and also drive up the cost.

There are no particular limitations on the NR. For example, natural rubbers commonly used in the tire industry can be used, such as SIR20, RSS #3, TSR20, deproteinized natural rubber (DPNR), and highly purified natural rubber (HPNR).

The NR content, based on 100% by mass of the rubber component, is preferably not less than 5% by mass, more preferably not less than 10% by mass, and still more preferably not less than 15% by mass. The abrasion resistance exhibits a declining trend when the NR content is less than 5% by mass. The NR content is preferably not more than 70% by mass, more preferably not more than 60% by mass, and still more preferably not more than 30% by mass. The wet-grip performance exhibits a declining trend when the NR content is more than 70% by mass.

There are no particular limitations on the BR, and commonly used BRs in the tire industry can be used, for example, high-cis BR such as BR1220 produced by Zeon Corporation and BR130B and BR150B produced by Ube Industries, Ltd., and BR containing syndiotactic polybutadiene crystals, such as VCR412 and VCR617 produced by Ube Industries, Ltd.

The BR content, based on 100% by mass of the rubber component, is preferably not less than 5% by mass, more preferably not less than 10% by mass, and still more preferably not less than 15% by mass. The abrasion resistance exhibits a declining trend when the BR content is less than 5% by mass. The BR content is preferably not more than 60% by mass, more preferably not more than 50% by mass, still more preferably not more than 35% by mass, further preferably not more than 30% by mass, and particularly preferably not more than 25% by mass. The wet-grip performance exhibits a declining trend when the BR content is more than 60% by mass.

The total content of NR and BR, based on 100% by mass of the rubber component, is preferably not less than 10% by mass, more preferably not less than 20% by mass, and still more preferably not less than 30% by mass. The abrasion resistance exhibits a declining trend when the total content is less than 10% by mass. The total content is preferably not more than 70% by mass, and more preferably not more than 50% by mass. The wet-grip performance exhibits a declining trend when the total content is more than 70% by mass.

The rubber composition of the present invention contains a compound represented by the following formula (1):

wherein R¹⁰¹ represents a hydrogen atom, a branched or unbranched C₁₋₃₀ alkyl group, a branched or unbranched C₂₋₃₀ alkenyl group, a branched or unbranched C₆₋₃₀ aryl group, or a hydroxy group; R¹⁰² and R¹⁰³ are the same as or different from each other and each represent a hydrogen atom, a branched or unbranched C₁₋₃₀ alkyl group, a branched or unbranched C₂₋₃₀ alkenyl group, a branched or unbranched C₂₋₃₀ alkynyl group, a branched or unbranched C₆₋₃₀ aryl group, or a group represented by formula (2) below, wherein a hydrogen atom of the alkyl group, alkenyl group, alkynyl group, or aryl group may be substituted by a hydroxy group or a carboxyl group; a pair of R¹⁰¹ and R¹⁰², a pair of R¹⁰¹ and R¹⁰³, or a pair of R¹⁰² and R¹⁰³ may form a cyclic structure; and d₁ represents an integer of 0 to 8,

wherein R¹⁰⁴ represents a branched or unbranched C₁₋₃₀ alkylene group; R¹⁰⁵ represents a hydrogen atom, a branched or unbranched C₁₋₃₀ alkyl group, a branched or unbranched C₂₋₃₀ alkenyl group, a branched or unbranched C₆₋₃₀ aryl group, or a hydroxy group; and d₂ represents an integer of 0 to 10.

Examples of the branched or unbranched C₁₋₃₀ (preferably C₃₋₂₅, more preferably C₁₀₋₂₀ still more preferably C₁₅₋₂₀) alkyl group encompassed by R¹⁰¹ include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an iso-butyl group, a sec-butyl group, a tert-butyl group, a pentyl group, a hexyl group, a heptyl group, a 2-ethylhexyl group, an octyl group, a nonyl group, a decyl group, an undecyl group, a dodecyl group, a tridecyl group, a tetradecyl group, a pentadecyl group, and an octadecyl group.

Examples of the branched or unbranched C₃₋₃₀ (preferably C₃₋₂₅, more preferably C₁₀₋₂₀, still more preferably C₁₅₋₂₀) alkenyl group encompassed by R¹⁰¹ include a vinyl group, a 1-propenyl group, a 2-propenyl group, a 1-butenyl group, a 2-butenyl group, a 1-pentenyl group, a 2-pentenyl group, a 1-hexenyl group, a 2-hexenyl group, a 1-octenyl group, a decenyl group, an undecenyl group, a dodecenyl group, a tridecenyl group, a tetradecenyl group, a pentadecenyl group, and an octadecenyl group.

Examples of the branched or unbranched C₆₋₃₀ (preferably C₆₋₁₀) aryl group encompassed by R¹⁰¹ include a phenyl group, a tolyl group, a xylyl group, a naphthyl group, and a biphenyl group.

R¹⁰¹ is preferably a hydrogen atom, a branched or unbranched C₁₋₃₀ alkyl group, or a hydroxy (—OH) group, and more preferably the alkyl group.

Examples of the branched or unbranched C₁₋₃₀ (preferably C₁₋₂₅, more preferably C₁₋₂₀, still more preferably C₁₋₁₀, particularly preferably C₁₋₅) alkyl group encompassed by R¹⁰² and R¹⁰³ include the same groups as the branched or unbranched C₁₋₃₀ alkyl groups mentioned above for R¹⁰¹.

Examples of the branched or unbranched C₂₋₃₀ (preferably C₂₋₂₅, more preferably C₂₋₂₀, still more preferably C₂₋₁₀, particularly preferably C₂₋₅) alkenyl group encompassed by R¹⁰² and R¹⁰³ include the same groups as the branched or unbranched C₂₋₃₀ alkenyl groups mentioned above for R¹⁰¹.

Examples of the branched or unbranched C₂₋₃₀ (preferably C₂₋₂₅, more preferably C₂₋₂₀, still more preferably C₂₋₁₀, particularly preferably C₂₋₅) alkynyl group encompassed by R¹⁰² and R¹⁰³ include an ethynyl group, a propynyl group, a butynyl group, a pentynyl group, a hexynyl group, an heptynyl group, an octynyl group, a nonynyl group, a decynyl group, an undecynyl group, and dodecynyl group.

Examples of the branched or unbranched C₆₋₃₀ (preferably C₆₋₁₀) aryl group encompassed by R¹⁰² and R¹⁰³ include the same groups as the branched or unbranched C₆₋₃₀ aryl groups mentioned above for R¹¹.

R¹⁰² and R¹⁰³ are each independently preferably a hydrogen atom, a branched or unbranched C₁₋₃₀ alkyl group, a branched or unbranched C₁₋₃₀ alkyl group substituted by a hydroxy group or a carboxyl group, a branched or unbranched C₆₋₃₀ aryl group substituted by a hydroxy group or a carboxyl group, or a group represented by formula (2) above, more preferably the alkyl group or the alkyl group substituted by a hydroxy group or a carboxyl group, and are still more preferably a combination of the alkyl group and the alkyl group substituted by a hydroxy group or a carboxyl group.

Here, d₁ represents an integer of 0 to 8, and is preferably an integer of 0 to 3, and more preferably 0, in view of achieving the effects of the present invention better.

Examples of the branched or unbranched C₁₋₃₀ (preferably C₁₋₁₅, more preferably C₁₋₃) alkylene group encompassed by R¹⁰⁴ include a methylene group, an ethylene group, a propylene group, a butylene group, a pentylene group, a hexylene group, a heptylene group, an octylene group, a nonylene group, a decylene group, an undecylene group, a dodecylene group, a tridecylene group, a tetradecylene group, pentadecylene group, a hexadecylene group, a heptadecylene group, and an octadecylene group.

Examples of the branched or unbranched C₁₋₃₀ (preferably C₃₋₂₅, more preferably C₁₀₋₂₀) alkyl group encompassed by R¹⁰⁵ include the same groups as the branched or unbranched C₁₋₃₀ alkyl groups mentioned above for R¹⁰¹.

Examples of the branched or unbranched C₂₋₃₀ (preferably C₃₋₂₅, more preferably C₁₀₋₂₀) alkenyl group encompassed by R¹⁰⁵ include the same groups as the branched or unbranched C₂₋₃₀ alkenyl groups mentioned above for R¹⁰¹.

Examples of the branched or unbranched C₆₋₃₀ (preferably C₆₋₁₀) aryl group encompassed by R¹⁰⁵ include the same groups as the branched or unbranched C₆₋₃₀ aryl groups mentioned above for R¹⁰¹.

R¹⁰⁵ is preferably a branched or unbranched C₁₋₃₀ alkyl group.

Here, d₂ represents an integer of 0 to 10, and is preferably an integer of 0 to 3, and more preferably 0, in view of achieving the effects of the present invention better.

Examples of the compound represented by the above formula (1) include N,N-dimethylformamide, octadecanamide, N-(4-hydroxyphenyl)octadecanamide, ε-caprolactam, sarcosine, N-lauroyl sarcosine, N-octadecyl sarcosine, N,N′-ethylene bisoctadecanamide, and N-(1-oxooctadecyl)sarcosine. These may be used alone or two or more may be used in combination.

The amount of the compound represented by formula (I), expressed per 100 parts by mass of silica, is preferably not less than 0.1 parts by mass, more preferably not less than 1.5 parts by mass, still more preferably not less than 2 parts by mass, further preferably not less than 2.5 parts by mass, and particularly preferably not less than 3.5 parts by mass. The addition of the compound represented by formula (1) in an amount of less than 0.1 parts by mass may fail to produce its effects sufficiently. The amount of the compound, expressed per 100 parts by mass of silica, is preferably not more than 20 parts by mass, more preferably not more than 10 parts by mass, still more preferably not more than 8 parts by mass, further preferably not more than 5.5 parts by mass, particularly preferably not more than 4 parts by mass, and most preferably not more than 3.5 parts by mass. If the amount of the compound exceeds 20 parts by mass, the hardness of the vulcanizate may decrease, resulting in deterioration of handling stability.

An amino acid derivative is preferably added in addition to the compound represented by formula (1) in the present invention. This enables to enhance the dispersibility of silica so that the effects of improving the properties can be increased.

In the case of adding an amino acid derivative in addition to the compound represented by formula (1), HT254 (produced by Schill+Seilacher GmbH) or similar products available in the market may be used as a mixture of the compound represented by formula (1) and the amino acid derivative.

The total amount of the compound represented by formula (1) and the amino acid derivative, expressed per 100 parts by mass of silica, is preferably not less than 0.2 parts by mass, more preferably not less than 1.5 parts by mass, still more preferably not less than 2 parts by mass, further preferably not less than 2.5 parts by mass, and particularly preferably not less than 3.5 parts by mass. The addition of the compound represented by formula (1) and the amino acid derivative in a total amount of less than 0.2 parts by mass may fail to produce its effects sufficiently. The total amount, expressed per 100 parts by mass of silica, is preferably not more than 20 parts by mass, more preferably not more than 10 parts by mass, still more preferably not more than 8 parts by mass, further preferably not more than 5.5 parts by mass, particularly preferably not more than 4 parts by mass, and most preferably not more than 3.5 parts by mass. If the total amount exceeds 20 parts by mass, the hardness of the vulcanizate may decrease, resulting in deterioration of handling stability.

The rubber composition of the present invention characteristically incorporates silica as a reinforcing agent. The amount (content) of silica, expressed per 100 parts by mass of the rubber component, is 5 to 150 parts by mass. The abrasion resistance tends to be unsatisfactory when the amount of silica is less than 5 parts by mass, whereas the processability tends to deteriorate when the amount of silica exceeds 150 parts by mass. The amount of silica is preferably not less than 10 parts by mass, more preferably not less than 15 parts by mass, and still more preferably not less than 45 parts by mass, and is also preferably not more than 120 parts by mass, and more preferably not more than 100 parts by mass.

The silica may be used alone, or two or more kinds of silica may be used in combination.

The silica content, based on a total of 100% by mass of silica and carbon black, is preferably not less than 60% by mass, and more preferably not less than 85% by mass, and is also preferably not more than 98% by mass, and more preferably not more than 95% by mass. The fuel economy, wet-grip performance, abrasion resistance, and processability can be enhanced to high levels in a balanced manner when the silica content is in the foregoing range.

The silica preferably has a nitrogen adsorption specific surface area (N₂SA) of not less than 40 m²/g, more preferably not less than 50 m²/g, still more preferably not less than 60 m²/g, and particularly preferably not less than 150 m²/g. The silica preferably has a N₂SA of not more than 400 m²/g, more preferably not more than 360 m²/g, still more preferably not more than 300 m²/g, and particularly preferably not more than 200 m²/g. If the silica has a nitrogen adsorption specific surface area of less than 40 m²/g, a little reinforcing effect is likely to be obtained and the abrasion resistance tends to be reduced. The silica having a N₂SA of more than 400 m²/g is likely to have poor dispersibility which tends to cause increased hysteresis loss and therefore reduced fuel economy.

The nitrogen adsorption specific surface area of silica is a value measured by the BET method in accordance with ASTM D3037-81.

The rubber composition of the present invention preferably contains a silane coupling agent together with silica. In view of enhancing the reinforcing effect, the silane coupling agent is preferably a silane coupling agent containing a sulfide group such as bis(3-triethoxysilylpropyl)tetrasulfide or 3-trimethoxysilylpropylbenzothiazolyl tetrasulfide, or a silane coupling agent containing a mercapto group such as 3-mercaptopropyltrimethoxysilane, and is more preferably a silane coupling agent containing a mercapto group. In general, the use of a silane coupling agent containing a mercapto group tends to reduce the processability; in contrast, in the present invention in which the compound represented by formula (1) is used, good processability can surely be obtained even when a silane coupling agent containing a mercapto group is used.

The silane coupling agent containing a mercapto group may suitably be a compound represented by formula (3) below, and/or a compound containing a linking unit A represented by formula (4) below and a linking unit B represented by formula (5) below,

wherein R²⁰¹ to 8²⁰³ may be the same as or different from one another, and R²⁰¹ to R²⁰³ each represent a branched or unbranched C₁₋₁₂ alkyl group, a branched or unbranched C₁₋₁₂ alkoxy group, or a group represented by —O—(R²¹¹—O)_(b)—R²¹² where b R²¹¹s may be the same as or different from one another and b R²¹¹s each represent a branched or unbranched C₁₋₃₀ divalent hydrocarbon group; R²¹² represents a branched or unbranched C₁₋₃₀ alkyl group, a branched or unbranched C₂₋₃₀ alkenyl group, a C₆₋₃₀ aryl group, or a C₇₋₃₀ aralkyl group; and b represents an integer of 1 to 30; and R²⁰⁴ represents a branched or unbranched C₁₋₆ alkylene group;

wherein R³⁰¹ represents a hydrogen atom, a halogen atom, a branched or unbranched C₁₋₃₀ alkyl group, a branched or unbranched C₂₋₃₀ alkenyl group, a branched or unbranched C₂₋₃₀ alkynyl group, or the alkyl group in which a terminal hydrogen atom is substituted by a hydroxy group or a carboxyl group; R³⁰² represents a branched or unbranched C₁₋₃₀ alkylene group, a branched or unbranched C₂₋₃₀ alkenylene group, or a branched or unbranched C₂₋₃₀ alkynylene group; and R³⁰¹ and R³⁰² together may form a cyclic structure.

The following explains the compound represented by formula (3).

The addition of a silane coupling agent represented by formula (3) enables to further enhance the wet-grip performance and the performance in terms of rolling resistance (fuel economy).

R²⁰¹ to R²⁰³ each independently represent a branched or unbranched C₁₋₁₂ alkyl group, a branched or unbranched C₁₋₁₂ alkoxy group, or a group represented by —O— (R²¹¹—O)_(b)—R²¹². In view of achieving the effects of the present invention better, preferably at least one of R²⁰¹ to R²⁰³ is a group represented by —O—(R²¹¹—O)_(b)—R²¹², and more preferably two of R²⁰¹ to R²⁰³ are groups represented by —O—(R²¹¹—O)_(b)—R²¹² and the other one is a branched of unbranched C₁₋₁₂ alkoxy group.

Examples of the branched or unbranched C₁₋₁₂ (preferably C₁₋₅) alkyl group encompassed by R²⁰¹ to R²⁰³ include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an iso-butyl group, a sec-butyl group, a tert-butyl group, a pentyl group, a hexyl group, a heptyl group, a 2-ethylhexyl group, an octyl group, and a nonyl group.

Examples of the branched or unbranched C₁₋₁₂ (preferably C₁₋₅) alkoxy group encompassed by R²⁰¹ to R²⁰³ include a methoxy group, an ethoxy group, an n-propoxy group, an isopropoxy group, an n-butoxy group, an iso-butoxy group, a sec-butoxy group, a tert-butoxy group, a pentyloxy group, a hexyloxy group, a heptyloxy group, a 2-ethylhexyloxy group, an octyloxy group, and a nonyloxy group.

R²¹¹ in the group: —O—(R²¹¹—O)_(b)—R²¹² encompassed by R²⁰¹ to R²⁰³ represents a branched or unbranched C₁₋₃₀ (preferably C₁₋₁₅, more preferably C₁₋₃) divalent hydrocarbon group.

Examples of the hydrocarbon group include branched or unbranched C₁₋₃₀ alkylene groups, branched or unbranched C₂₋₃₀ alkenylene groups, branched or unbranched C₂₋₃₀ alkynylene groups, and C₆₋₃₀ arylene groups. Branched or unbranched C₁₋₃₀ alkylene groups are preferred among the examples.

Examples of the branched or unbranched C₁₋₃₀ (preferably C₁₋₁₅, more preferably C₁₋₃) alkylene group encompassed by R²¹¹ include a methylene group, an ethylene group, a propylene group, a butylene group, a pentylene group, a hexylene group, a heptylene group, an octylene group, a nonylene group, a decylene group, an undecylene group, a dodecylene group, a tridecylene group, a tetradecylene group, a pentadecylene group, a hexadecylene group, a heptadecylene group, and an octadecylene group.

Examples of the branched or unbranched C₂₋₃₀ (preferably C₂₋₁₅, more preferably C₂₋₃) alkenylene group encompassed by R²¹¹ include a vinylene group, a 1-propenylene group, a 2-propenylene group, a 1-butenylene group, a 2-butenylene group, a 1-pentenylene group, a 2-pentenylene group, a 1-hexenylene group, a 2-hexenylene group, and a 1-octenylene group.

Examples of the branched or unbranched C₂₋₃₀ (preferably C₂₋₁₅, more preferably C₂₋₃) alkynylene group encompassed by R²¹¹ include an ethynylene group, a propynylene group, a butynylene group, a pentynylene group, a hexynylene group, a heptynylene group, an octynylene group, a nonynylene group, a decynylene group, an undecynylene group, and a dodecynylene group.

Examples of the C₆₋₃₀ (preferably C₆₋₁₅) arylene group encompassed by R²¹¹ include a phenylene group, a tolylene group, a xylylene group, and a naphthylene group.

Here, b represents an integer of 1 to 30 (preferably 2 to 20, more preferably 3 to 7, and still more preferably 5 or 6).

R²¹² represents a branched or unbranched C₁₋₃₀ alkyl group, a branched or unbranched C₂₋₃₀ alkenyl group, a C₆₋₃₀ aryl group, or a C₇₋₃₀ aralkyl group. R²¹² is especially preferably a branched or unbranched C₁₋₃₀ alkyl group.

Examples of the branched or unbranched C₁₋₃₀ (preferably C₃₋₂₅, more preferably C₁₀₋₁₅) alkyl group encompassed by R²¹² include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an iso-butyl group, a sec-butyl group, a tert-butyl group, a pentyl group, a hexyl group, a heptyl group, a 2-ethylhexyl group, an octyl group, a nonyl group, a decyl group, an undecyl group, a dodecyl group, a tridecyl group, a tetradecyl group, a pentadecyl group, and an octadecyl group.

Examples of the branched or unbranched C₂₋₃₀ (preferably C₃₋₂₅, more preferably C₁₀₋₁₅) alkenyl group encompassed by R²¹² include a vinyl group, a 1-propenyl group, a 2-propenyl group, a 1-butenyl group, a 2-butenyl group, a 1-pentenyl group, a 2-pentenyl group, a 1-hexenyl group, a 2-hexenyl group, a 1-octenyl group, a decenyl group, an undecenyl group, a dodecenyl group, a tridecenyl group, a tetradecenyl group, a pentadecenyl group, and an octadecenyl group.

Examples of the C₆₋₃₀ (preferably C₁₀₋₂₀) aryl group encompassed by R²¹² include a phenyl group, a tolyl group, a xylyl group, a naphthyl group, and a biphenyl group.

Examples of the C₇₋₃₀ (preferably C₁₀₋₂₀ aralkyl group encompassed by R²¹² include a benzyl group and a phenethyl group.

Specific examples of the group represented by —O—-(R²¹¹—O)_(b)—R²¹² include —O— (C₂H₄—O)₅—C₁₁H₂₃, —O—(C₂H₄—O)₅—C₁₂H₂₅, —O—(C₂H₄—O)₅—C₁₃H₂₇, —O—(C₂H₄—O)₅—C₁₄H₂₉, —O—(C₂H₄—O)₅—O₁₅H₃₁, —O—(C₂H₄—O)₃—C₁₃H₂₇, —O—(C₂H₄—O)₄—C₁₃H₂₇, —O—(C₂H₄—O)₆—C₁₃H₂₇ and —O—(C₂H₄—O)₇—C₁₃H₂₇. Among the examples, —O—(C₂H₄—O)₅—C₁₁H₂₃, —O—(C₂H₄—O)₅—C₁₃H₂₇, —O—(C₂H₄—O)₅—C₁₅H₃₁, and —O—(C₂H₄—O)₆—C₁₃H₂₇ are preferred.

Examples of the branched or unbranched C₁₋₆ (preferably C₁₋₅) alkylene group encompassed by R²⁰⁴ include the same groups as the branched or unbranched C₁₋₃₀ alkylene groups mentioned above for R²¹¹.

Examples of the compound represented by formula (3) include 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyl-trimethoxysilane, 2-mercaptoethyltriethoxysilane, and a compound represented by the following formula (Si363 produced by Evonik Degussa). Use of the compound represented by the following formula is preferred. These may be used alone or two or more may be used in combination.

The following explains the compound containing a linking unit A represented by formula (4) and a linking unit B represented by formula (5).

When the compound containing a linking unit A represented by formula (4) and a linking unit B represented by formula (5) is used, the increase in viscosity during the processing can be suppressed compared to the case where polysulfide silane such as bis-(3-triethoxysilylpropyl)tetrasulfide is used. This is presumably because, since the sulfide moiety of the linking unit A is a C—S—C bond, the compound is thermally more stable than tetrasulfide or disulfide, and thus the Mooney viscosity is less likely to increase.

Moreover, the decrease in the scorch time can be suppressed compared to the case where mercapto silane such as 3-mercaptopropyltrimethoxysilane is used. This is presumably because, though the linking unit B has a mercapto silane structure, the —C₇H₁₅ moiety of the linking unit A covers a —SH group of the linking unit B, as a result of which the SH group is less likely to react with polymers. Thus, good processability can be achieved even when a larger amount of a vulcanization accelerator is used, or when SBR, which is easily scorched, is mixed.

From the viewpoint of enhancing the effects of suppressing the viscosity increase during the processing and of suppressing the decrease in the scorch time as mentioned above, the linking unit A content in the silane coupling agent having the foregoing structure is preferably not less than 30 mol %, and more preferably not less than 50 mol %, and is also preferably not more than 99 mol %, and more preferably not more than 90 mol %. The linking unit B content is preferably not less than 1 mol %, more preferably not less than 5 mol %, and still more preferably not less than 10 mol %, and is also preferably not more than 70 mol %, more preferably not more than 65 mol %, and still more preferably not more than 55 mol %. The total content of the linking unit A and the linking unit B is preferably not less than 95 mol %, more preferably not less than 98 mol %, and particularly preferably 100 mol %.

The content of the linking unit A or B is the amount including the linking unit A or B that is present at the terminal of the silane coupling agent, if any. In the case where the linking unit A or B is present at the terminal of the silane coupling agent, its form is not particularly limited as long as it forms a unit corresponding to the formula (4) representing the linking unit A or the formula (5) representing the linking unit B.

Examples of the halogen atom encompassed by R³⁰¹ include chlorine, bromine, and fluorine.

Examples of the branched or unbranched C₁₋₃₀ alkyl group encompassed by R³⁰¹ and R³⁰² include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an iso-butyl group, a sec-butyl group, a tert-butyl group, a pentyl group, a hexyl group, a heptyl group, a 2-ethylhexyl group, an octyl group, a nonyl group, and a decyl group. The alkyl group preferably has 1 to 12 carbon atoms.

Examples of the branched or unbranched C₁₋₃₀ alkylene group encompassed by R³⁰¹ and R³⁰² include an ethylene group, a propylene group, a butylene group, a pentylene group, a hexylene group, a heptylene group, an octylene group, a nonylene group, a decylene group, an undecylene group, a dodecylene group, a tridecylene group, a tetradecylene group, a pentadecylene group, a hexadecylene group, a heptadecylene group, and an octadecylene group. The alkylene group preferably has 1 to 12 carbon atoms.

Examples of the branched or unbranched C₂₋₃₀ alkenyl group encompassed by R³⁰¹ and R³⁰² include a vinyl group, a 1-propenyl group, a 2-propenyl group, a 1-butenyl group, a 2-butenyl group, a 1-pentenyl group, a 2-pentenyl group, a 1-hexenyl group, a 2-hexenyl group, and a 1-octenyl group. The alkenyl group preferably has 2 to 12 carbon atoms.

Examples of the branched or unbranched C₂₋₃₀ alkenylene group encompassed by R³⁰¹ and R³⁰² include a vinylene group, a 1-propenylene group, a 2-propenylene group, a 1-butenylene group, a 2-butenylene group, a 1-pentenylene group, a 2-pentenylene group, a 1-hexenylene group, a 2-hexenylene group, and a 1-octenylene group. The alkenylene group preferably has 2 to 12 carbon atoms.

Examples of the branched or unbranched C₂₋₃₀ alkynyl group encompassed by R³⁰¹ and R³⁰² include an ethynyl group, a propynyl group, a butynyl group, a pentynyl group, a hexynyl group, a heptynyl group, an octynyl group, a nonynyl group, a decynyl group, an undecynyl group, and a dodecynyl group. The alkynyl group preferably has 2 to 12 carbon atoms.

Examples of the branched or unbranched C₂₋₃₀ alkynylene group encompassed by R³⁰² and R³⁰² include an ethynylene group, a propynylene group, a butynylene group, a pentynylene group, a hexynylene group, a heptynylene group, an octynylene group, a nonynylene group, a decynylene group, an undecynylene group, and a dodecynylene group. The alkynylene group preferably has 2 to 12 carbon atoms.

In the compound containing the linking unit A represented by formula (4) and the linking unit B represented by formula (5), the total number of repetitions (x+y) of the number of repetitions (x) of the linking unit A and the number of repetitions (y) of the linking unit B is preferably in the range of 3 to 300. When the total number of repetitions is in that range, the —C₇H₁₅ moiety of the linking unit A covers the mercaptosilane of the linking unit B, which enables to suppress the decrease in the scorch time and to secure favorable reactivity to silica and the rubber component.

Examples of the compound containing the linking unit A represented by formula (4) and the linking unit B represented by formula (5) include NXT-Z30, NXT-Z45, and NXT-Z60 (produced by Momentive Performance Materials). These may be used alone, or two or more of these may be used in combination.

The silane coupling agent content, expressed per 100 parts by mass of silica, is preferably not less than 0.5 parts by mass, more preferably not less than 1.5 parts by mass, still more preferably not less than 2.5 parts by mass, further preferably not less than 4 parts by mass, particularly preferably not less than 6 parts by mass, and most preferably not less than 8 parts by mass. The silane coupling agent content of less than 0.5 parts by mass may make it difficult to favorably disperse silica. The silane coupling agent content is preferably not more than 20 parts by mass, more preferably not more than 15 parts by mass, and still more preferably not more than 10 parts by mass. The silane coupling agent content in excess of 20 parts by mass may fail to give an improvement effect commensurate with the added amount, which may result in unnecessary cost increase. In addition, the scorch time is likely to be reduced so that the processability tends to deteriorate in the kneading or extrusion process.

Known additives may be used as the additives. Examples of the additives include vulcanizing agents such as sulfur; vulcanization accelerators such as thiazole vulcanization accelerators, thiuram vulcanization accelerators, sulfenamide vulcanization accelerators, and guanidine vulcanization accelerators; vulcanization activators such as stearic acid and zinc oxide; organoperoxides; fillers such as carbon black, calcium carbonate, talc, alumina, clay, aluminum hydroxide, and mica; processing aids such as extender oils and lubricants; and antioxidants.

Examples of the carbon black include furnace blacks (furnace carbon blacks) such as SAF, ISAF, HAF, MAF, FEF, SRF, GPF, APF, FF, CF, SCF, and ECF; acetylene blacks (acetylene carbon blacks); thermal blacks (thermal carbon blacks) such as FT and MT; channel blacks (channel carbon blacks) such as EPC, MPC, and CC; and graphite. These may be used alone or two or more may be used in combination. In view of enhancing the fuel economy, wet-grip performance, abrasion resistance, and processability to high levels in a balanced manner, the carbon black content, per 100 parts by mass of the rubber component, is preferably not less than 1 part by mass, and more preferably not less than 3 parts by mass. The carbon black content is also preferably not more than 60 parts by mass, more preferably not more than 50 parts by mass, still more preferably not more than 30 parts by mass, and particularly preferably not more than 10 parts by mass.

The carbon black preferably has a nitrogen adsorption specific surface area (N₂SA) of not less than 5 m²/g, more preferably not less than 30 m²/g, still more preferably not less than 50 m²/g, and particularly preferably not less than 70 m²/g. The nitrogen adsorption specific surface area is also preferably not more than 250 m²/g, more preferably not more than 200 m²/g, and still more preferably not more than 150 m²/g. The carbon black preferably has a dibutyl phthalate (DBP) absorption of not less than 5 mL/100 g, more preferably not less than 80 mL/100 g. The dibutyl phthalate (DBP) absorption is also preferably not more than 300 mL/100 g, and more preferably not more than 180 mL/100 g. If the carbon black has a N₂SA or DBP absorption of less than the corresponding lower limit of the range, then a little reinforcing effect is likely to be obtained and the abrasion resistance tends to be reduced. If the N₂SA or DBP absorption exceeds the corresponding upper limit of the range, the dispersibility is likely to be poor and the hysteresis loss is likely to increase so that the fuel economy tends to be reduced. The nitrogen adsorption specific surface area is measured in accordance with ASTM D4820-93, and the DBP absorption is measured in accordance with ASTM D2414-93. Applicable commercial products are available under the trade names SEAST 6, SEAST 7HM, and SEAST KH from Tokai Carbon Co., Ltd., and under the trade names CK3 and Special Black 4A from Evonik Degussa, and so forth.

Examples of the extender oil include aromatic mineral oils (viscosity-gravity constant (VGC value)=0.900 to 1.049), naphthenic mineral oils (VGC value=0.850 to 0.899), and paraffinic mineral oils (VGC value=0.790 to 0.849). The polycyclic aromatic content of the extender oil is preferably less than 3% by mass, and more preferably less than 1% by mass. The polycyclic aromatic content is measured based on the British Institute of Petroleum method 346/92. Moreover, the aromatic compound content (CA) of the extender oil is preferably not less than 20% by mass. Two or more of these extender oils may be used in combination.

Examples of the vulcanization accelerator include thiazole vulcanization accelerators such as 2-mercaptobenzothiazole, dibenzothiazyl disulfide, and N-cyclohexyl-2-benzothiazylsulfenamide; thiuram vulcanization accelerators such as tetramethylthiuram monosulfide and tetramethylthiuram disulfide; sulfenamide vulcanization accelerators such as N-cyclohexyl-2-benzothiazolesulfenamide, N-t-butyl-2-benzothiazolesulfenamide, N-oxyethylene-2-benzothiazolesulfenamide, N-oxyethylene-2-benzothiazolesulfenamide, and N,N′-diisopropyl-2-benzothiazolesulfenamide; and guanidine vulcanization accelerators such as diphenylguanidine, di-ortho-tolylguanidine, and ortho-tolylbiguanidine. The amount thereof used, expressed per 100 parts by mass of the rubber component, is preferably 0.1 to 5 parts by mass, and more preferably 0.2 to 3 parts by mass.

A known method can be used to mix the conjugated diene polymer with another rubber material, additives and so forth to prepare the rubber composition. For example, a method can be used in which the ingredients are kneaded using a known mixer, e.g., a roll mixer or a Banbury mixer.

With regard to the kneading conditions during the incorporation of additives other than vulcanizing agents and vulcanization accelerators, the kneading temperature is typically 50 to 200° C., preferably 80 to 190° C., and the kneading time is typically 30 seconds to 30 minutes, preferably 1 to 30 minutes.

During the incorporation of a vulcanizing agent and vulcanization accelerator, the kneading temperature is typically not more than 100° C. and is preferably in the range of room temperature to 80° C. The composition in which the vulcanizing agent and vulcanization accelerator have been incorporated is typically subjected to a vulcanizing treatment such as press vulcanization before use. The vulcanization temperature is typically 120 to 200° C., preferably 140 to 180° C.

The rubber composition of the present invention has an excellent balance among fuel economy, wet-grip performance, abrasion resistance, and processability, and can provide a significant improvement in these properties.

The rubber composition of the present invention can be suitably used for various tire components and is particularly well suited for treads.

The pneumatic tire of the present invention can be produced by a usual method using the aforementioned rubber composition. Specifically, the rubber composition that incorporates various additives as necessary, before vulcanization, is extrusion processed into the shape of a tire tread, for example, and is then arranged by a usual method and assembled with other tire components in a tire building machine to form an unvulcanized tire. This unvulcanized tire is heat-pressed in a vulcanizer to produce a pneumatic tire of the present invention.

The pneumatic tire of the present invention can be suitably used as a tire for passenger vehicles and for trucks/buses (heavy-load tire).

EXAMPLES

The present invention is described referring to the following examples.

The property evaluations of polymers were carried out using the following methods.

1. Vinyl Bond Content (Unit: Mol %)

The vinyl bond content of a polymer was determined by infrared spectroscopic analysis from the strength of the absorption in the vicinity of 910 cm⁻¹, which is an absorption peak for a vinyl group.

2. Styrene Unit Content (Unit: % by Mass)

The styrene unit content of a polymer was determined from the refractive index according to JIS K6383 (1995).

3. Molecular Weight Distribution (Mw/Mn)

The weight-average molecular weight (Mw) and the number-average molecular weight (Mn) of a polymer were measured by gel permeation chromatography (GPC) under the conditions (1) to (8) described below. The molecular weight distribution (Mw/Mn) of the polymer was then determined from the measured Mw and Mn.

-   (1) instrument: HLC-8020 produced by Tosoh Corporation -   (2) separation columns: 2×GMH-XL in series, produced by Tosoh     Corporation -   (3) measurement temperature: 40° C. -   (4) carrier: tetrahydrofuran -   (5) flow rate: 0.6 mL/minute -   (6) quantity of injection: 5 μL -   (7) detector: differential refractometer -   (8) molecular weight standards: polystyrene standards

Production Example 1 Synthesis of Polymer 1

The interior of a 20-L stainless steel polymerization reactor was washed and dried, and then replaced with dry nitrogen. Next, 10.2 kg of hexane (specific gravity=0.68 g/cm³), 547 g of 1,3-butadiene, 173 g of styrene, 6.1 mL of tetrahydrofuran, and 5.0 mL of ethylene glycol diethyl ether were introduced into the polymerization reactor. Thereafter, 11.1 mmol of bis(diethylamino)methylvinylsilane in cyclohexane and 13.1 mmol of n-butyllithium in n-hexane were further introduced to initiate polymerization.

The 1,3-butadiene and styrene were copolymerized for 3 hours under stirring at a rate of 130 rpm and a temperature within the polymerization reactor of 65° C. while the monomers were continuously fed into the polymerization reactor. During the entire polymerization, the amount of 1,3-butadiene fed was 821 g, and the amount of styrene fed was 259 g.

The resulting polymer solution was stirred at a rate of 130 rpm, and 11.1 mmol of 3-diethylaminopropyl-triethoxysilane was added thereto, followed by stirring for 15 minutes. Then, 20 mL of a hexane solution containing 0.54 mL of methanol was added to the polymer solution, and the polymer solution was stirred for additional 5 minutes.

To the resulting polymer solution were added 1.8 g of 2-tert-butyl-6-(3-tert-butyl-2-hydroxy-5-methylbenzyl)-4-methylphenyl acrylate (trade name: Sumilizer GM, produced by Sumitomo Chemical Co., Ltd.) and 0.9 g of pentaerythrityl tetrakis(3-laurylthiopropionate) (trade name: Sumilizer TP-D, produced by Sumitomo Chemical Co., Ltd.). Then, Polymer 1 was recovered from the polymer solution by steam stripping. Table 1 shows the evaluation results of Polymer 1. The content of the constituent unit represented by formula (I) in the polymer, as calculated from the amounts of raw materials introduced and the amounts of raw materials fed into the polymerization reactor, was 0.006 mmol/g-polymer per unit mass of the polymer.

Production Example 2 Synthesis of Polymer 2

The interior of a 20-L stainless steel polymerization reactor was washed and dried, and then replaced with dry nitrogen. Next, 10.2 kg of hexane (specific gravity=0.68 g/cm³), 547 g of 1,3-butadiene, 173 g of styrene, 6.1 mL of tetrahydrofuran, and 5.0 mL of ethylene glycol diethyl ether were introduced into the polymerization reactor. Thereafter, 11.1 mmol of bis(diethylamino)methylvinylsilane in cyclohexane and 13.1 mmol of n-butyllithium in n-hexane were further introduced to initiate polymerization.

The 1,3-butadiene and styrene were copolymerized for 3 hours under stirring at a rate of 130 rpm and a temperature within the polymerization reactor of 65° C. while the monomers were continuously fed into the polymerization reactor. During the entire polymerization, the amount of 1,3-butadiene fed was 821 g, and the amount of styrene fed was 259 g.

The resulting polymer solution was stirred at a rate of 130 rpm, and 11.1 mmol of 3-diethylaminopropyl-triethoxysilane was added thereto, followed by stirring for 15 minutes. Then, 20 mL of a hexane solution containing 0.54 mL of methanol was added to the polymer solution, and the polymer solution was stirred for additional 5 minutes.

To the resulting polymer solution were added 1.8 g of 2-tert-butyl-6-(3-tert-butyl-2-hydroxy-5-methylbenzyl)-4-methylphenyl acrylate (trade name: Sumilizer GM, produced by Sumitomo Chemical Co., Ltd.) and 0.9 g of pentaerythrityl tetrakis(3-laurylthiopropionate) (trade name: Sumilizer TP-D, produced by Sumitomo Chemical Co., Ltd.). Then, the polymer solution was evaporated at ordinary temperature over 24 hours, and further dried under reduced pressure at 55° C. for 12 hours, so that Polymer 2 was obtained. Table 1 shows the evaluation results of Polymer 2. The content of the constituent unit represented by formula (I) in the polymer, as calculated from the amounts of raw materials introduced and the amounts of raw materials fed into the polymerization reactor, was 0.006 mmol/g-polymer per unit mass of the polymer.

Production Example 3 Synthesis of Polymer 3 (unmodified SBR)

The interior of a 20-L stainless steel polymerization reactor was washed and dried, and then replaced with dry nitrogen. Next, 10.2 kg of hexane (specific gravity=0.68 g/cm³), 547 g of 1,3-butadiene, 173 g of styrene, 6.1 mL of tetrahydrofuran, and 5.0 mL of ethylene glycol diethyl ether were introduced into the polymerization reactor. Thereafter, 13.1 mmol of n-butyllithium in n-hexane was further introduced to initiate polymerization.

The 1,3-butadiene and styrene were copolymerized for 3 hours under stirring at a rate of 130 rpm and a temperature within the polymerization reactor of 65° C. while the monomers were continuously fed into the polymerization reactor. During the entire polymerization, the amount of 1,3-butadiene fed was 821 g, and the amount of styrene fed was 259 g.

Then, 20 mL of a hexane solution containing 0.54 mL of methanol was added to the polymer solution, and the polymer solution was stirred for additional 5 minutes.

To the resulting polymer solution were added 1.8 g of 2-tert-butyl-6-(3-tert-butyl-2-hydroxy-5-methylbenzyl)-4-methylphenyl acrylate (trade name: Sumilizer GM, produced by Sumitomo Chemical Co., Ltd.) and 0.9 g of pentaerythrityl tetrakis(3-laurylthiopropionate) (trade name: Sumilizer TP-D, produced by Sumitomo Chemical Co., Ltd.). Then, Polymer 3 was recovered from the polymer solution by steam stripping. Table 1 shows the evaluation results of Polymer 3. Since the compound represented by formula (IX) was not used in the synthesis of Polymer 3, Polymer 3 did not contain the constituent unit represented by formula (I).

TABLE 1 Polymer 1 2 3 Styrene unit content (% by mass) 25 25 24 Vinyl bond content (mol %) 59 60 58 Molecular weight distribution (Mw/Mn) 1.2 1.2 1.1

Production Example 4 Synthesis of Polymer 4

The interior of a 20-L stainless steel polymerization reactor was washed and dried, and then replaced with dry nitrogen. Next, 10.2 kg of hexane (specific gravity=0.68 g/cm³), 547 g of 1,3-butadiene, 173 g of styrene, 6.1 mL of tetrahydrofuran, and 5.0 mL of ethylene glycol diethyl ether were introduced into the polymerization reactor. Thereafter, 11.0 mmol of bis(diethylamino)methylvinylsilane in cyclohexane and 14.3 mmol of n-butyllithium in n-hexane were further introduced to initiate polymerization.

The 1,3-butadiene and styrene were copolymerized for 3 hours under stirring at a rate of 130 rpm and a temperature within the polymerization reactor of 65° C. while the monomers were continuously fed into the polymerization reactor. During the entire polymerization, the amount of 1,3-butadiene fed was 821 g, and the amount of styrene fed was 259 g.

The resulting polymer solution was then stirred at a rate of 130 rpm, and 11.0 mmol of 1,3-dimethyl-2-imidazolidinone was added thereto, followed by stirring for 15 minutes. Then, 20 mL of a hexane solution containing 0.54 mL of methanol was added to the polymer solution, and the polymer solution was stirred for additional 5 minutes.

To the resulting polymer solution were added 1.8 g of 2-tert-butyl-6-(3-tert-butyl-2-hydroxy-5-methylbenzyl)-4-methylphenyl acrylate (trade name: Sumilizer GM, produced by Sumitomo Chemical Co., Ltd.) and 0.9 g of pentaerythrityl tetrakis(3-laurylthiopropionate) (trade name: Sumilizer TP-D, produced by Sumitomo Chemical Co., Ltd.). Then, Polymer 4 was recovered from the polymer solution by steam stripping. Table 2 shows the evaluation results of Polymer 4. The content of the constituent unit represented by formula (I) in the polymer, as calculated from the amounts of raw materials introduced and the amounts of raw materials fed into the polymerization reactor, was 0.006 mmol/g-polymer per unit mass of the polymer.

Production Example 5 Synthesis of Polymer 5

The interior of a 20-L stainless steel polymerization reactor was washed and dried, and then replaced with dry nitrogen. Next, 10.2 kg of hexane (specific gravity=0.68 g/cm³), 547 g of 1,3-butadiene, 173 g of styrene, 6.1 mL of tetrahydrofuran, and 5.0 mL of ethylene glycol diethyl ether were introduced into the polymerization reactor. Thereafter, 11.1 mmol of bis(diethylamino)methylvinylsilane in cyclohexane and 14.3 mmol of n-butyllithium in n-hexane were further introduced to initiate polymerization.

The 1,3-butadiene and styrene were copolymerized for 3 hours under stirring at a rate of 130 rpm and a temperature within the polymerization reactor of 65° C. while the monomers were continuously fed into the polymerization reactor. During the entire polymerization, the amount of 1,3-butadiene fed was 821 g, and the amount of styrene fed was 259 g.

The resulting polymer solution was then stirred at a rate of 130 rpm, and 11.0 mmol of 1,3-dimethyl-2-imidazolidinone was added thereto, followed by stirring for 15 minutes. Then, 20 mL of a hexane solution containing 0.54 mL of methanol was added to the polymer solution, and the polymer solution was stirred for additional 5 minutes.

To the resulting polymer solution were added 1.8 g of 2-tert-butyl-6-(3-tert-butyl-2-hydroxy-5-methylbenzyl)-4-methylphenyl acrylate (trade name: Sumilizer GM, produced by Sumitomo Chemical Co., Ltd.) and 0.9 g of pentaerythrityl tetrakis(3-laurylthiopropionate) (trade name: Sumilizer TP-D, produced by Sumitomo Chemical Co., Ltd.). Then, the polymer solution was evaporated at ordinary temperature over 24 hours, and further dried under reduced pressure at 55° C. for 12 hours, so that Polymer 5 was obtained. Table 2 shows the evaluation results of Polymer 5. The content of the constituent unit represented by formula (I) in the polymer, as calculated from the amounts of raw materials introduced and the amounts of raw materials fed into the polymerization reactor, was 0.006 mmol/g-polymer per unit mass of the polymer.

TABLE 2 Polymer 4 5 Styrene unit content (% by mass) 25 25 Vinyl bond content (mol %) 60 62 Molecular weight distribution (Mw/Mn) 1.2 1.2

Production Example 6 Synthesis of Polymer 6

The interior of a 20-L stainless steel polymerization reactor was washed and dried, and then replaced with dry nitrogen. Next, 10.2 kg of hexane (specific gravity=0.68 g/cm³), 547 g of 1,3-butadiene, 173 g of styrene, 6.1 mL of tetrahydrofuran, and 5.0 mL of ethylene glycol diethyl ether were introduced into the polymerization reactor. Thereafter, 10.5 mmol of bis(diethylamino)methylvinylsilane in cyclohexane and 14.9 mmol of n-butyllithium in n-hexane were further introduced to initiate polymerization.

The 1,3-butadiene and styrene were copolymerized for 3 hours under stirring at a rate of 130 rpm and a temperature within the polymerization reactor of 65° C. while the monomers were continuously fed into the polymerization reactor. During the entire polymerization, the amount of 1,3-butadiene fed was 821 g, and the amount of styrene fed was 259 g.

The resulting polymer solution was then stirred at a rate of 130 rpm, and 10.5 mmol of N-(3-dimethylaminopropyl)acrylamide was added thereto, followed by stirring for 15 minutes. Then, 20 mL of a hexane solution containing 0.54 mL of methanol was added to the polymer solution, and the polymer solution was stirred for additional 5 minutes.

To the resulting polymer solution were added 1.8 g of 2-tert-butyl-6-(3-tert-butyl-2-hydroxy-5-methylbenzyl)-4-methylphenyl acrylate (trade name: Sumilizer GM, produced by Sumitomo Chemical Co., Ltd.) and 0.9 g of pentaerythrityl tetrakis(3-laurylthiopropionate) (trade name: Sumilizer TP-D, produced by Sumitomo Chemical Co., Ltd.). Then, Polymer 6 was recovered from the polymer solution by steam stripping. Table 3 shows the evaluation results of Polymer 6. The content of the constituent unit represented by formula (I) in the polymer, as calculated from the amounts of raw materials introduced and the amounts of raw materials fed into the polymerization reactor, was 0.006 mmol/g-polymer per unit mass of the polymer.

Production Example 7 Synthesis of Polymer 7

The interior of a 20-L stainless steel polymerization reactor was washed and dried, and then replaced with dry nitrogen. Next, 10.2 kg of hexane (specific gravity=0.68 g/cm³), 547 g of 1,3-butadiene, 173 g of styrene, 6.1 mL of tetrahydrofuran, and 5.0 mL of ethylene glycol diethyl ether were introduced into the polymerization reactor. Thereafter, 12.9 mmol of n-butyllithium in n-hexane was further introduced, and the 1,3-butadiene and styrene were copolymerized for 0.83 hours. The polymerization was carried out under stirring at a rate of 130 rpm and a temperature within the polymerization reactor of 65° C. while the monomers were continuously fed into the polymerization reactor.

After the 0.83-hour polymerization, 10.5 mmol of bis(diethylamino)methylvinylsilane in cyclohexane was introduced into the polymerization reactor under stirring at a rate of 130 rpm and a temperature within the polymerization reactor of 65° C.

Next, the monomers were continuously fed into the polymerization reactor, and the 1,3-butadiene and styrene were copolymerized for 1.67 hours. The polymerization was carried out under stirring at a rate of 130 rpm and a temperature within the polymerization reactor of 65° C. During the entire polymerization, the amount of 1,3-butadiene fed was 821 g, and the amount of styrene fed was 259 g.

The resulting polymer solution was then stirred at a rate of 130 rpm, and 10.5 mmol of N-(3-dimethylaminopropyl)acrylamide was added thereto, followed by stirring for 15 minutes. Then, 20 mL of a hexane solution containing 0.54 mL of methanol was added to the polymer solution, and the polymer solution was stirred for additional 5 minutes.

To the resulting polymer solution were added 1.8 g of 2-tert-butyl-6-(3-tert-butyl-2-hydroxy-5-methylbenzyl)-4-methylphenyl acrylate (trade name: Sumilizer GM, produced by Sumitomo Chemical Co., Ltd.) and 0.9 g of pentaerythrityl tetrakis(3-laurylthiopropionate) (trade name: Sumilizer TP-D, produced by Sumitomo Chemical Co., Ltd.). Then, Polymer 7 was recovered from the polymer solution by steam stripping. Table 3 shows the evaluation results of Polymer 7. The content of the constituent unit represented by formula (I) in the polymer, as calculated from the amounts of raw materials introduced and the amounts of raw materials fed into the polymerization reactor, was 0.006 mmol/g-polymer per unit mass of the polymer.

Production Example 8 Synthesis of Polymer 8

The interior of a 20-L stainless steel polymerization reactor was washed and dried, and then replaced with dry nitrogen. Next, 10.2 kg of hexane (specific gravity=0.68 g/cm³), 547 g of 1,3-butadiene, 173 g of styrene, 6.1 mL of tetrahydrofuran, and 5.0 mL of ethylene glycol diethyl ether were introduced into the polymerization reactor. Thereafter, 10.5 mmol of bis(diethylamino)methylvinylsilane in cyclohexane and 13.4 mmol of n-butyllithium in n-hexane were further introduced, and the 1,3-butadiene and styrene were copolymerized for one hour. The polymerization was carried out under stirring at a rate of 130 rpm and a temperature within the polymerization reactor of 65° C. while the monomers were continuously fed into the polymerization reactor.

After the one hour polymerization, 10.5 mmol of bis(diethylamino)methylvinylsilane in cyclohexane was introduced into the polymerization reactor under stirring at a rate of 130 rpm and a temperature within the polymerization reactor of 65° C.

Next, the monomers were continuously fed into the polymerization reactor, and the 1,3-butadiene and styrene were copolymerized for 0.5 hours. The polymerization was carried out under stirring at a rate of 130 rpm and a temperature within the polymerization reactor of 65° C.

After the 0.5-hour polymerization, 10.5 mmol of bis(diethylamino)methylvinylsilane in cyclohexane was introduced into the polymerization reactor under stirring at a rate of 130 rpm and a temperature within the polymerization reactor of 65° C.

Next, the monomers were continuously fed into the polymerization reactor, and the 1,3-butadiene and styrene were copolymerized for 1.5 hours. The polymerization was carried out under stirring at a rate of 130 rpm and a temperature within the polymerization reactor of 65° C. During the entire polymerization, the amount of 1,3-butadiene fed was 821 g, and the amount of styrene fed was 259 g.

The resulting polymer solution was then stirred at a rate of 130 rpm, and 10.5 mmol of N-(3-dimethylaminopropyl)acrylamide was added thereto, followed by stirring for 15 minutes.

Then, 20 mL of a hexane solution containing 0.54 mL of methanol was added to the polymer solution, and the polymer solution was stirred for additional 5 minutes. To the resulting polymer solution were added 1.8 g of 2-tert-butyl-6-(3-tert-butyl-2-hydroxy-5-methylbenzyl)-4-methylphenyl acrylate (trade name: Sumilizer GM, produced by Sumitomo Chemical Co., Ltd.) and 0.9 g of pentaerythrityl tetrakis(3-laurylthiopropionate) (trade name: Sumilizer TP-D, produced by Sumitomo Chemical Co., Ltd.). Then, Polymer 8 was recovered from the polymer solution by steam stripping. Table 3 shows the evaluation results of Polymer 8. The content of the constituent unit represented by formula (I) in the polymer, as calculated from the amounts of raw materials introduced and the amounts of raw materials fed into the polymerization reactor, was 0.017 mmol/g-polymer per unit mass of the polymer.

Production Example 9 Synthesis of Polymer 9

The interior of a 20-L stainless steel polymerization reactor was washed and dried, and then replaced with dry nitrogen. Next, 10.2 kg of hexane (specific gravity=0.68 g/cm³), 547 g of 1,3-butadiene, 173 g of styrene, 6.1 mL of tetrahydrofuran, and 5.0 mL of ethylene glycol diethyl ether were introduced into the polymerization reactor. Thereafter, 10.5 mmol of bis(di(n-butyl)amino)methylvinylsilane in cyclohexane and 13.4 mmol of n-butyllithium in n-hexane were further introduced to initiate polymerization.

The 1,3-butadiene and styrene were copolymerized for 3 hours under stirring at a rate of 130 rpm and a temperature within the polymerization reactor of 65° C. while the monomers were continuously fed into the polymerization reactor. During the entire polymerization, the amount of 1,3-butadiene fed was 821 g, and the amount of styrene fed was 259 g.

The resulting polymer solution was then stirred at a rate of 130 rpm, and 10.5 mmol of N-(3-dimethylaminopropyl)acrylamide was added thereto, followed by stirring for 15 minutes. Then, 20 mL of a hexane solution containing 0.54 mL of methanol was added to the polymer solution, and the polymer solution was stirred for additional 5 minutes.

To the resulting polymer solution were added 1.8 g of 2-tert-butyl-6-(3-tert-butyl-2-hydroxy-5-methylbenzyl)-4-methylphenyl acrylate (trade name: Sumilizer GM, produced by Sumitomo Chemical Co., Ltd.) and 0.9 g of pentaerythrityl tetrakis(3-laurylthiopropionate) (trade name: Sumilizer TP-D, produced by Sumitomo Chemical Co., Ltd.). Then, Polymer 9 was recovered from the polymer solution by steam stripping. Table 3 shows the evaluation results of Polymer 9. The content of the constituent unit represented by formula (I) in the polymer, as calculated from the amounts of raw materials introduced and the amounts of raw materials fed into the polymerization reactor, was 0.006 mmol/g-polymer per unit mass of the polymer.

Production Example 10 Synthesis of Polymer 10

The interior of a 5-L stainless steel polymerization reactor was washed and dried, and then replaced with dry nitrogen. Next, 2.55 kg of hexane (specific gravity=0.68 g/cm³), 137 g of 1,3-butadiene, 43 g of styrene, 1.5 mL of tetrahydrofuran, and 1.2 mL of ethylene glycol diethyl ether were introduced into the polymerization reactor. Thereafter, 3.6 mmol of n-butyllithium in n-hexane was further introduced, and the 1,3-butadiene and styrene were copolymerized for 2.5 hours. The polymerization was carried out under stirring at a rate of 130 rpm and a temperature within the polymerization reactor of 65° C. while the monomers were continuously fed into the polymerization reactor. The amount of 1,3-butadiene fed was 205 g, and the amount of styrene fed was 65 g.

After the 2.5-hour polymerization, 2.8 mmol of bis(diethylamino)methylvinylsilane in cyclohexane was introduced into the polymerization reactor under stirring at a rate of 130 rpm and a temperature within the polymerization reactor of 65° C., followed by stirring for 30 minutes.

Next, 20 mL of a hexane solution containing 0.14 mL of methanol was introduced into the polymerization reactor, and the polymer solution was stirred for 5 minutes.

To the resulting polymer solution were added 1.8 g of 2-tert-butyl-6-(3-tert-butyl-2-hydroxy-5-methylbenzyl)-4-methylphenyl acrylate (trade name: Sumilizer GM, produced by Sumitomo Chemical Co., Ltd.) and 0.9 g of pentaerythrityl tetrakis(3-laurylthiopropionate) (trade name: Sumilizer TP-D, produced by Sumitomo Chemical Co., Ltd.). Then, Polymer 10 was recovered from the polymer solution by steam stripping. Table 3 shows the evaluation results of Polymer 10. The content of the constituent unit represented by formula (I) in the polymer, as calculated from the amounts of raw materials introduced and the amounts of raw materials fed into the polymerization reactor, was 0.006 mmol/g-polymer per unit mass of the polymer.

Production Example 11 Synthesis of Polymer 11

The interior of a 20-L stainless steel polymerization reactor was washed and dried, and then replaced with dry nitrogen. Next, 10.2 kg of hexane (specific gravity=0.68 g/cm³), 547 g of 1,3-butadiene, 173 g of styrene, 6.1 mL of tetrahydrofuran, and 5.0 mL of ethylene glycol diethyl ether were introduced into the polymerization reactor. Thereafter, 10.5 mmol of bis(diethylamino)methylvinylsilane in cyclohexane and 14.9 mmol of n-butyllithium in n-hexane were further introduced to initiate polymerization.

The 1,3-butadiene and styrene were copolymerized for 3 hours under stirring at a rate of 130 rpm and a temperature within the polymerization reactor of 65° C. while the monomers were continuously fed into the polymerization reactor. During the entire polymerization, the amount of 1,3-butadiene fed was 821 g, and the amount of styrene fed was 259 g.

Then, 20 mL of a hexane solution containing 0.54 mL of methanol was added to the polymer solution, and the polymer solution was stirred for additional 5 minutes.

To the resulting polymer solution were added 1.8 g of 2-tert-butyl-6-(3-tert-butyl-2-hydroxy-5-methylbenzyl)-4-methylphenyl acrylate (trade name: Sumilizer GM, produced by Sumitomo Chemical Co., Ltd.) and 0.9 g of pentaerythrityl tetrakis(3-laurylthiopropionate) (trade name: Sumilizer TP-D, produced by Sumitomo Chemical Co., Ltd.). Then, Polymer 11 was recovered from the polymer solution by steam stripping. Table 3 shows the evaluation results of Polymer 11. The content of the constituent unit represented by formula (I) in the polymer, as calculated from the amounts of raw materials introduced and the amounts of raw materials fed into the polymerization reactor, was 0.006 mmol/g-polymer per unit mass of the polymer.

Production Example 12 Synthesis of Polymer 12

The interior of a 20-L stainless steel polymerization reactor was washed and dried, and then replaced with dry nitrogen. Next, 10.2 kg of hexane (specific gravity=0.68 g/cm³), 547 g of 1,3-butadiene, 173 g of styrene, 6.1 mL of tetrahydrofuran, and 5.0 mL of ethylene glycol diethyl ether were introduced into the polymerization reactor. Thereafter, 14.9 mmol of n-butyllithium in n-hexane was further introduced to initiate polymerization.

The 1,3-butadiene and styrene were copolymerized for 3 hours under stirring at a rate of 130 rpm and a temperature within the polymerization reactor of 65° C. while the monomers were continuously fed into the polymerization reactor. During the entire polymerization, the amount of 1,3-butadiene fed was 821 g, and the amount of styrene fed was 259 g.

The resulting polymer solution was then stirred at a rate of 130 rpm, and 10.5 mmol of N-(3-dimethylaminopropyl)acrylamide was added thereto, followed by stirring for 15 minutes. Then, 20 mL of a hexane solution containing 0.54 mL of methanol was added to the polymer solution, and the polymer solution was stirred for additional 5 minutes.

To the resulting polymer solution were added 1.8 g of 2-tert-butyl-6-(3-tert-butyl-2-hydroxy-5-methylbenzyl)-4-methylphenyl acrylate (trade name: Sumilizer GM, produced by Sumitomo Chemical Co., Ltd.) and 0.9 g of pentaerythrityl tetrakis(3-laurylthiopropionate) (trade name: Sumilizer TP-D, produced by Sumitomo Chemical Co., Ltd.). Then, Polymer 12 was recovered from the polymer solution by steam stripping. Table 3 shows the evaluation results of Polymer 12. Since the compound represented by formula (IX) was not used in the synthesis of Polymer 12, Polymer 12 did not contain the constituent unit represented by formula (I).

Production Example 13 Synthesis of Polymer 13

The interior of a 20-L stainless steel polymerization reactor was washed and dried, and then replaced with dry nitrogen. Next, 10.2 kg of hexane (specific gravity=0.68 g/cm³), 547 g of 1,3-butadiene, 173 g of styrene, 6.1 mL of tetrahydrofuran, and 5.0 mL of ethylene glycol diethyl ether were introduced into the polymerization reactor. Thereafter, 14.9 mmol of n-butyllithium in n-hexane was further introduced to initiate polymerization.

The 1,3-butadiene and styrene were copolymerized for 3 hours under stirring at a rate of 130 rpm and a temperature within the polymerization reactor of 65° C. while the monomers were continuously fed into the polymerization reactor. During the entire polymerization, the amount of 1,3-butadiene fed was 821 g, and the amount of styrene fed was 259 g.

Then, 20 mL of a hexane solution containing 0.54 mL of methanol was added to the polymer solution, and the polymer solution was stirred for additional 5 minutes.

To the resulting polymer solution were added 1.8 g of 2-tert-butyl-6-(3-tert-butyl-2-hydroxy-5-methylbenzyl)-4-methylphenyl acrylate (trade name: Sumilizer GM, produced by Sumitomo Chemical Co., Ltd.) and 0.9 g of pentaerythrityl tetrakis(3-laurylthiopropionate) (trade name: Sumilizer TP-D, produced by Sumitomo Chemical Co., Ltd.). Then, Polymer 13 was recovered from the polymer solution by steam stripping. Table 3 shows the evaluation results of Polymer 13. Since the compound represented by formula (IX) was not used in the synthesis of Polymer 13, Polymer 13 did not contain the constituent unit represented by formula (I).

Production Example 14 Synthesis of Polymer 14

The interior of a 20-L stainless steel polymerization reactor was washed and dried, and then replaced with dry nitrogen. Next, 10.2 kg of hexane (specific gravity=0.68 g/cm³), 547 g of 1,3-butadiene, 173 g of styrene, 6.1 mL of tetrahydrofuran, and 5.0 mL of ethylene glycol diethyl ether were introduced into the polymerization reactor. Thereafter, 10.5 mmol of bis(diethylamino)methylvinylsilane in cyclohexane and 14.9 mmol of n-butyllithium in n-hexane were further introduced to initiate polymerization.

The 1,3-butadiene and styrene were copolymerized for 3 hours under stirring at a rate of 130 rpm and a temperature within the polymerization reactor of 65° C. while the monomers were continuously fed into the polymerization reactor. During the entire polymerization, the amount of 1,3-butadiene fed was 821 g, and the amount of styrene fed was 259 g.

The resulting polymer solution was then stirred at a rate of 130 rpm, and 10.5 mmol of N-(3-dimethylaminopropyl)acrylamide was added thereto, followed by stirring for 15 minutes. Then, 20 mL of a hexane solution containing 0.54 mL of methanol was added to the polymer solution, and the polymer solution was stirred for additional 5 minutes.

To the resulting polymer solution were added 1.8 g of 2-tert-butyl-6-(3-tert-butyl-2-hydroxy-5-methylbenzyl)-4-methylphenyl acrylate (trade name: Sumilizer GM, produced by Sumitomo Chemical Co., Ltd.) and 0.9 g of pentaerythrityl tetrakis(3-laurylthiopropionate) (trade name: Sumilizer TP-D, produced by Sumitomo Chemical Co., Ltd.). Then, the polymer solution was evaporated at ordinary temperature over 24 hours, and further dried under reduced pressure at 55° C. for 12 hours, so that Polymer 14 was obtained. Table 3 shows the evaluation results of Polymer 14. The content of the constituent unit represented by formula (I) in the polymer, as calculated from the amounts of raw materials introduced and the amounts of raw materials fed into the polymerization reactor, was 0.006 mmol/g-polymer per unit mass of the polymer.

TABLE 3 Polymer 6 7 8 9 10 11 12 13 14 Styrene unit content (% by mass) 25 24 24 25 25 25 24 24 25 Vinyl bond content (mol %) 59 60 58 59 59 60 60 58 59 Molecular weight distribution (Mw/Mn) 1.2 1.1 1.1 1.3 1.1 1.2 1.1 1.1 1.2

Production Example 15 Synthesis of Polymer 15

The interior of a 20-L stainless steel polymerization reactor was washed and dried, and then replaced with dry nitrogen. Next, 10.2 kg of hexane (specific gravity=0.68 g/cm³), 547 g of 1,3-butadiene, 173 g of styrene, 6.1 mL of tetrahydrofuran, and 5.0 mL of ethylene glycol diethyl ether were introduced into the polymerization reactor. Thereafter, 16.0 mmol of bis(diethylamino)methylvinylsilane in cyclohexane and 18.5 mmol of n-butyllithium in n-hexane were further introduced to initiate polymerization.

The 1,3-butadiene and styrene were copolymerized for 3 hours under stirring at a rate of 130 rpm and a temperature within the polymerization reactor of 65° C. while the monomers were continuously fed into the polymerization reactor. During the entire polymerization, the amount of 1,3-butadiene fed was 821 g, and the amount of styrene fed was 259 g.

The resulting polymer solution was then stirred at a rate of 130 rpm, and 4.0 mmol of 1,3,5-tris(3-trimethoxysilylpropyl)isocyanurate was added thereto, followed by stirring for 15 minutes. Then, 20 mL of a hexane solution containing 0.80 mL of methanol was added to the polymer solution, and the polymer solution was stirred for additional 5 minutes.

To the resulting polymer solution were added 1.8 g of 2-tert-butyl-6-(3-tert-butyl-2-hydroxy-5-methylbenzyl)-4-methylphenyl acrylate (trade name: Sumilizer GM, produced by Sumitomo Chemical Co., Ltd.) and 0.9 g of pentaerythrityl tetrakis(3-laurylthiopropionate) (trade name: Sumilizer TP-D, produced by Sumitomo Chemical Co., Ltd.). Then, Polymer 15 was recovered from the polymer solution by steam stripping. Table 4 shows the evaluation results of Polymer 15. The content of the constituent unit represented by formula (I) in the polymer, as calculated from the amounts of raw materials introduced and the amounts of raw materials fed into the polymerization reactor, was 0.009 mmol/g-polymer per unit mass of the polymer.

Production Example 16 Synthesis of Polymer 16

The interior of a 20-L stainless steel polymerization reactor was washed and dried, and then replaced with dry nitrogen. Next, 10.2 kg of hexane (specific gravity=0.68 g/cm³), 547 g of 1,3-butadiene, 173 g of styrene, 6.1 mL of tetrahydrofuran, and 5.0 mL of ethylene glycol diethyl ether were introduced into the polymerization reactor. Thereafter, 17.3 mmol of n-butyllithium in n-hexane was further introduced, and the 1,3-butadiene and styrene were copolymerized for one hour. The polymerization was carried out under stirring at a rate of 130 rpm and a temperature within the polymerization reactor of 65° C. while the monomers were continuously fed into the polymerization reactor.

After the one hour polymerization, 14.4 mmol of bis(diethylamino)methylvinylsilane in cyclohexane was introduced into the polymerization reactor under stirring at a rate of 130 rpm and a temperature within the polymerization reactor of 65° C.

Next, the monomers were continuously fed into the polymerization reactor, and The 1,3-butadiene and styrene were copolymerized for 0.5 hours. The polymerization was carried out under stirring at a rate of 130 rpm and a temperature within the polymerization reactor of 65° C.

After the 0.5-hour polymerization, 14.4 mmol of bis(diethylamino)methylvinylsilane in cyclohexane was introduced into the polymerization reactor under stirring at a rate of 130 rpm and a temperature within the polymerization reactor of 65° C.

Next, the monomers were continuously fed into the polymerization reactor, and rhe 1,3-butadiene and styrene were copolymerized for 0.5 hours. The polymerization was carried out under stirring at a rate of 130 rpm and a temperature within the polymerization reactor of 65° C.

After the 0.5-hour polymerization, 14.4 mmol of bis(diethylamino)methylvinylsilane in cyclohexane was introduced into the polymerization reactor under stirring at a rate of 130 rpm and a temperature within the polymerization reactor of 65° C.

Next, the monomers were continuously fed into the polymerization reactor, and The 1,3-butadiene and styrene were copolymerized for 0.5 hours. The polymerization was carried out under stirring at a rate of 130 rpm and a temperature within the polymerization reactor of 65° C. During the entire polymerization, the amount of 1,3-butadiene fed was 821 g, and the amount of styrene fed was 259 g.

The resulting polymer solution was then stirred at a rate of 130 rpm, and 3.6 mmol of 1,3,5-tris(3-trimethoxysilylpropyl)isocyanurate was added thereto, followed by stirring for 15 minutes. Then, 20 mL of a hexane solution containing 0.80 mL of methanol was added to the polymer solution, and the polymer solution was stirred for additional 5 minutes.

To the resulting polymer solution were added 1.8 g of 2-tert-butyl-6-(3-tert-butyl-2-hydroxy-5-methylbenzyl)-4-methylphenyl acrylate (trade name: Sumilizer GM, produced by Sumitomo Chemical Co., Ltd.) and 0.9 g of pentaerythrityl tetrakis(3-laurylthiopropionate) (trade name: Sumilizer TP-D, produced by Sumitomo Chemical Co., Ltd.). Then, Polymer 16 was recovered from the polymer solution by steam stripping. Table 4 shows the evaluation results of Polymer 16. The content of the constituent unit represented by formula (I) in the polymer, as calculated from the amounts of raw materials introduced and the amounts of raw materials fed into the polymerization reactor, was 0.024 mmol/g-polymer per unit mass of the polymer.

Production Example 17 Synthesis of Polymer 17

The interior of a 5-L stainless steel polymerization reactor was washed and dried, and then replaced with dry nitrogen. Next, 2.55 kg of hexane (specific gravity=0.68 g/cm³), 137 g of 1,3-butadiene, 43 g of styrene, 1.5 mL of tetrahydrofuran, and 1.2 mL of ethylene glycol diethyl ether were introduced into the polymerization reactor. Thereafter, 3.6 mmol of n-butyllithium in n-hexane was further introduced, and the 1,3-butadiene and styrene were copolymerized for 2.5 hours. The polymerization was carried out under stirring at a rate of 130 rpm and a temperature within the polymerization reactor of 65° C. while the monomers were continuously fed into the polymerization reactor. The amount of 1,3-butadiene fed was 205 g, and the amount of styrene fed was 65 g.

After the 2.5-hour polymerization, 2.8 mmol of bis(diethylamino)methylvinylsilane in cyclohexane was introduced into the polymerization reactor under stirring at a rate of 130 rpm and a temperature within the polymerization reactor of 65° C., followed by stirring for 30 minutes.

Next, 20 mL of a hexane solution containing 0.14 mL of methanol was introduced into the polymerization reactor, and the polymer solution was stirred for 5 minutes.

To the resulting polymer solution were added 1.8 g of 2-tert-butyl-6-(3-tert-butyl-2-hydroxy-5-methylbenzyl)-4-methylphenyl acrylate (trade name: Sumilizer GM, produced by Sumitomo Chemical Co., Ltd.) and 0.9 g of pentaerythrityl tetrakis(3-laurylthiopropionate) (trade name: Sumilizer TP-D, produced by Sumitomo Chemical Co., Ltd.). Then, Polymer 17 was recovered from the polymer solution by steam stripping. Table 4 shows the evaluation results of Polymer 17. The content of the constituent unit represented by formula (I) in the polymer, as calculated from the amounts of raw materials introduced and the amounts of raw materials fed into the polymerization reactor, was 0.006 mmol/g-polymer per unit mass of the polymer.

Production Example 18 Synthesis of Polymer 18

The interior of a 20-L stainless steel polymerization reactor was washed and dried, and then replaced with dry nitrogen. Next, 10.2 kg of hexane (specific gravity=0.68 g/cm³), 547 g of 1,3-butadiene, 173 g of styrene, 6.1 mL of tetrahydrofuran, and 5.0 mL of ethylene glycol diethyl ether were introduced into the polymerization reactor. Thereafter, 16.0 mmol of bis(diethylamino)methylvinylsilane in cyclohexane and 18.5 mmol of n-butyllithium in n-hexane were further introduced to initiate polymerization.

The 1,3-butadiene and styrene were copolymerized for 3 hours under stirring at a rate of 130 rpm and a temperature within the polymerization reactor of 65° C. while the monomers were continuously fed into the polymerization reactor. During the entire polymerization, the amount of 1,3-butadiene fed was 821 g, and the amount of styrene fed was 259 g.

Then, 20 mL of a hexane solution containing 0.80 mL of methanol was added to the polymer solution, and the polymer solution was stirred for additional 5 minutes.

To the resulting polymer solution were added 1.8 g of 2-tert-butyl-6-(3-tert-butyl-2-hydroxy-5-methylbenzyl)-4-methylphenyl acrylate (trade name: Sumilizer GM, produced by Sumitomo Chemical Co., Ltd.) and 0.9 g of pentaerythrityl tetrakis(3-laurylthiopropionate) (trade name: Sumilizer TP-D, produced by Sumitomo Chemical Co., Ltd.). Then, Polymer 18 was recovered from the polymer solution by steam stripping. Table 4 shows the evaluation results of Polymer 18. The content of the constituent unit represented by formula (I) in the polymer, as calculated from the amounts of raw materials introduced and the amounts of raw materials fed into the polymerization reactor, was 0.009 mmol/g-polymer per unit mass of the polymer.

Production Example 19 Synthesis of Polymer 19

The interior of a 20-L stainless steel polymerization reactor was washed and dried, and then replaced with dry nitrogen. Next, 10.2 kg of hexane (specific gravity=0.68 g/cm³), 547 g of 1,3-butadiene, 173 g of styrene, 6.1 mL of tetrahydrofuran, and 5.0 mL of ethylene glycol diethyl ether were introduced into the polymerization reactor. Thereafter, 18.5 mmol of n-butyllithium in n-hexane was further introduced to initiate polymerization.

The 1,3-butadiene and styrene were copolymerized for 3 hours under stirring at a rate of 130 rpm and a temperature within the polymerization reactor of 65° C. while the monomers were continuously fed into the polymerization reactor. During the entire polymerization, the amount of 1,3-butadiene fed was 821 g, and the amount of styrene fed was 259 g.

The resulting polymer solution was then stirred at a rate of 130 rpm, and 4.0 mmol of 1,3,5-tris(3-trimethoxysilylpropyl)isocyanurate was added thereto, followed by stirring for 15 minutes. Then, 20 mL of a hexane solution containing 0.80 mL of methanol was added to the polymer solution, and the polymer solution was stirred for additional 5 minutes.

To the resulting polymer solution were added 1.8 g of 2-tert-butyl-6-(3-tert-butyl-2-hydroxy-5-methylbenzyl)-4-methylphenyl acrylate (trade name: Sumilizer GM, produced by Sumitomo Chemical Co., Ltd.) and 0.9 g of pentaerythrityl tetrakis(3-laurylthiopropionate) (trade name: Sumilizer TP-D, produced by Sumitomo Chemical Co., Ltd.). Then, Polymer 19 was recovered from the polymer solution by steam stripping. Table 4 shows the evaluation results of Polymer 19. Since the compound represented by formula (IX) was not used in the synthesis of Polymer 19, Polymer 19 did not contain the constituent unit represented by formula (I).

Production Example 20 Synthesis of Polymer 20

The interior of a 20-L stainless steel polymerization reactor was washed and dried, and then replaced with dry nitrogen. Next, 10.2 kg of hexane (specific gravity=0.68 g/cm³), 547 g of 1,3-butadiene, 173 g of styrene, 6.1 mL of tetrahydrofuran, and 5.0 mL of ethylene glycol diethyl ether were introduced into the polymerization reactor. Thereafter, 18.5 mmol of n-butyllithium in n-hexane was further introduced to initiate polymerization.

The 1,3-butadiene and styrene were copolymerized for 3 hours under stirring at a rate of 130 rpm and a temperature within the polymerization reactor of 65° C. while the monomers were continuously fed into the polymerization reactor. During the entire polymerization, the amount of 1,3-butadiene fed was 821 g, and the amount of styrene fed was 259 g.

Then, 20 mL of a hexane solution containing 0.80 mL of methanol was added to the polymer solution, and the polymer solution was stirred for additional 5 minutes.

To the resulting polymer solution were added 1.8 g of 2-tert-butyl-6-(3-tert-butyl-2-hydroxy-5-methylbenzyl)-4-methylphenyl acrylate (trade name: Sumilizer GM, produced by Sumitomo Chemical Co., Ltd.) and 0.9 g of pentaerythrityl tetrakis(3-laurylthiopropionate) (trade name: Sumilizer TP-D, produced by Sumitomo Chemical Co., Ltd.). Then, Polymer 20 was recovered from the polymer solution by steam stripping. Table 4 shows the evaluation results of Polymer 20. Since the compound represented by formula (IX) was not used in the synthesis of Polymer 20, Polymer 20 did not contain the constituent unit represented by formula (I).

Production Example 21 Synthesis of Polymer 21

The interior of a 20-L stainless steel polymerization reactor was washed and dried, and then replaced with dry nitrogen. Next, 10.2 kg of hexane (specific gravity=0.68 g/cm³), 547 g of 1,3-butadiene, 173 g of styrene, 6.1 mL of tetrahydrofuran, and 5.0 mL of ethylene glycol diethyl ether were introduced into the polymerization reactor. Thereafter, 16.0 mmol of bis(diethylamino)methylvinylsilane in cyclohexane and 18.5 mmol of n-butyllithium in n-hexane were further introduced to initiate polymerization.

The 1,3-butadiene and styrene were copolymerized for 3 hours under stirring at a rate of 130 rpm and a temperature within the polymerization reactor of 65° C. while the monomers were continuously fed into the polymerization reactor. During the entire polymerization, the amount of 1,3-butadiene fed was 821 g, and the amount of styrene fed was 259 g.

The resulting polymer solution was then stirred at a rate of 130 rpm, and 4.0 mmol of 1,3,5-tris(3-trimethoxysilylpropyl)isocyanurate was added thereto, followed by stirring for 15 minutes. Then, 20 mL of a hexane solution containing 0.80 mL of methanol was added to the polymer solution, and the polymer solution was stirred for additional 5 minutes.

To the resulting polymer solution were added 1.8 g of 2-tert-butyl-6-(3-tert-butyl-2-hydroxy-5-methylbenzyl)-4-methylphenyl acrylate (trade name: Sumilizer GM, produced by Sumitomo Chemical Co., Ltd.) and 0.9 g of pentaerythrityl tetrakis(3-laurylthiopropionate) (trade name: Sumilizer TP-D, produced by Sumitomo Chemical Co., Ltd.). Then, the polymer solution was evaporated at ordinary temperature over 24 hours, and further dried under reduced pressure at 55° C. for 12 hours, so that Polymer 21 was obtained. Table 4 shows the evaluation results of Polymer 21. The content of the constituent unit represented by formula (I) in the polymer, as calculated from the amounts of raw materials introduced and the amounts of raw materials fed into the polymerization reactor, was 0.009 mmol/g-polymer per unit mass of the polymer.

Production Example 22 Synthesis of Polymer 22

The interior of a 20-L stainless steel polymerization reactor was washed and dried, and then replaced with dry nitrogen. Next, 10.2 kg of hexane (specific gravity=0.68 g/cm³), 547 g of 1,3-butadiene, 173 g of styrene, 6.1 mL of tetrahydrofuran, and 5.0 mL of ethylene glycol diethyl ether were introduced into the polymerization reactor. Thereafter, 16.0 mmol of bis(diethylamino)methylvinylsilane in cyclohexane and 18.5 mmol of n-butyllithium in n-hexane were further introduced to initiate polymerization.

The 1,3-butadiene and styrene were copolymerized for 3 hours under stirring at a rate of 130 rpm and a temperature within the polymerization reactor of 65° C. while the monomers were continuously fed into the polymerization reactor. During the entire polymerization, the amount of 1,3-butadiene fed was 821 g, and the amount of styrene fed was 259 g.

The resulting polymer solution was then stirred at a rate of 130 rpm, and 4.0 mmol of 3-(methoxy)propyltrimethoxysilane was added thereto, followed by stirring for 15 minutes. Then, 20 mL of a hexane solution containing 0.80 mL of methanol was added to the polymer solution, and the polymer solution was stirred for additional 5 minutes.

To the resulting polymer solution were added 1.8 g of 2-tert-butyl-6-(3-tert-butyl-2-hydroxy-5-methylbenzyl)-4-methylphenyl acrylate (trade name: Sumilizer GM, produced by Sumitomo Chemical Co., Ltd.) and 0.9 g of pentaerythrityl tetrakis(3-laurylthiopropionate) (trade name: Sumilizer TP-D, produced by Sumitomo Chemical Co., Ltd.). Then, Polymer 22 was recovered from the polymer solution by steam stripping. Table 4 shows the evaluation results of Polymer 22. The content of the constituent unit represented by formula (I) in the polymer, as calculated from the amounts of raw materials introduced and the amounts of raw materials fed into the polymerization reactor, was 0.009 mmol/g-polymer per unit mass of the polymer.

TABLE 4 Polymer 15 16 17 18 19 20 21 22 Styrene unit content (% by mass) 25 25 24 24 25 24 25 24 Vinyl bond content (mol %) 59 59 60 60 59 58 60 59 Molecular weight distribution (Mw/Mn) 1.5 1.6 1.1 1.2 1.3 1.1 1.5 1.4

Production Example 23 Synthesis of Polymer 23

The interior of a 20-L stainless steel polymerization reactor was washed and dried, and then replaced with dry nitrogen. Next, 10.2 kg of hexane (specific gravity=0.68 g/cm³), 547 g of 1,3-butadiene, 173 g of styrene, 6.1 mL of tetrahydrofuran, and 5.0 mL of ethylene glycol diethyl ether were introduced into the polymerization reactor. Thereafter, 11.5 mmol of bis(diethylamino)methylvinylsilane in cyclohexane and 14.1 mmol of n-butyllithium in n-hexane were further introduced to initiate polymerization.

The 1,3-butadiene and styrene were copolymerized for 3 hours under stirring at a rate of 130 rpm and a temperature within the polymerization reactor of 65° C. while the monomers were continuously fed into the polymerization reactor. During the entire polymerization, the amount of 1,3-butadiene fed was 821 g, and the amount of styrene fed was 259 g.

The resulting polymer solution was then stirred at a rate of 130 rpm, and 11.5 mmol of N,N-dimethylformamide dimethyl acetal was added thereto, followed by stirring for 15 minutes. Then, 20 mL of a hexane solution containing 0.54 mL of methanol was added to the polymer solution, and the polymer solution was stirred for additional 5 minutes.

To the resulting polymer solution were added 1.8 g of 2-tert-butyl-6-(3-tert-butyl-2-hydroxy-5-methylbenzyl)-4-methylphenyl acrylate (trade name: Sumilizer GM, produced by Sumitomo Chemical Co., Ltd.) and 0.9 g of pentaerythrityl tetrakis(3-laurylthiopropionate) (trade name: Sumilizer TP-D, produced by Sumitomo Chemical Co., Ltd.). Then, Polymer 23 was recovered from the polymer solution by steam stripping. Table 5 shows the evaluation results of Polymer 23. The content of the constituent unit represented by formula (I) in the polymer, as calculated from the amounts of raw materials introduced and the amounts of raw materials fed into the polymerization reactor, was 0.006 mmol/g-polymer per unit mass of the polymer.

Production Example 24 Synthesis of Polymer 24

The interior of a 20-L stainless steel polymerization reactor was washed and dried, and then replaced with dry nitrogen. Next, 10.2 kg of hexane (specific gravity=0.68 g/cm³), 547 g of 1,3-butadiene, 173 g of styrene, 6.1 mL of tetrahydrofuran, and 5.0 mL of ethylene glycol diethyl ether were introduced into the polymerization reactor. Thereafter, 14.1 mmol of n-butyllithium in n-hexane was further introduced, and the 1,3-butadiene and styrene were copolymerized for one hour. The polymerization was carried out under stirring at a rate of 130 rpm and a temperature within the polymerization reactor of 65° C. while the monomers were continuously fed into the polymerization reactor.

After the one hour polymerization, 11.0 mmol of bis(diethylamino)methylvinylsilane in cyclohexane was introduced into the polymerization reactor under stirring at a rate of 130 rpm and a temperature within the polymerization reactor of 65° C.

Next, the monomers were continuously fed into the polymerization reactor, and the 1,3-butadiene and styrene were copolymerized for 0.5 hours. The polymerization was carried out under stirring at a rate of 130 rpm and a temperature within the polymerization reactor of 65° C.

After the 0.5-hour polymerization, 11.0 mmol of bis(diethylamino)methylvinylsilane in cyclohexane was introduced into the polymerization reactor under stirring at a rate of 130 rpm and a temperature within the polymerization reactor of 65° C.

Next, the monomers were continuously fed into the polymerization reactor, and the 1,3-butadiene and styrene were copolymerized for 0.5 hours. The polymerization was carried out under stirring at a rate of 130 rpm and a temperature within the polymerization reactor of 65° C.

After the 0.5-hour polymerization, 11.0 mmol of bis(diethylamino)methylvinylsilane in cyclohexane was introduced into the polymerization reactor under stirring at a rate of 130 rpm and a temperature within the polymerization reactor of 65° C.

Next, the monomers were continuously fed into the polymerization reactor, and the 1,3-butadiene and styrene were copolymerized for 0.5 hours. The polymerization was carried out under stirring at a rate of 130 rpm and a temperature within the polymerization reactor of 65° C. During the entire polymerization, the amount of 1,3-butadiene fed was 821 g, and the amount of styrene fed was 259 g.

The resulting polymer solution was then stirred at a rate of 130 rpm, and 11.0 mmol of N,N-dimethylformamide dimethyl acetal was added thereto, followed by stirring for 15 minutes. Then, 20 mL of a hexane solution containing 0.54 mL of methanol was added to the polymer solution, and the polymer solution was stirred for additional 5 minutes.

To the resulting polymer solution were added 1.8 g of 2-tert-butyl-6-(3-tert-butyl-2-hydroxy-5-methylbenzyl)-4-methylphenyl acrylate (trade name: Sumilizer GM, produced by Sumitomo Chemical Co., Ltd.) and 0.9 g of pentaerythrityl tetrakis(3-laurylthiopropionate) (trade name: Sumilizer TP-D, produced by Sumitomo Chemical Co., Ltd.). Then, Polymer 24 was recovered from the polymer solution by steam stripping. Table 5 shows the evaluation results of Polymer 24. The content of the constituent unit represented by formula (I) in the polymer, as calculated from the amounts of raw materials introduced and the amounts of raw materials fed into the polymerization reactor, was 0.018 mmol/g-polymer per unit mass of the polymer.

Production Example 25 Synthesis of Polymer 25

The interior of a 5-L stainless steel polymerization reactor was washed and dried, and then replaced with dry nitrogen. Next, 2.55 kg of hexane (specific gravity=0.68 g/cm³), 137 g of 1,3-butadiene, 43 g of styrene, 1.5 mL of tetrahydrofuran, and 1.2 mL of ethylene glycol diethyl ether were introduced into the polymerization reactor. Thereafter, 3.6 mmol of n-butyllithium in n-hexane was further introduced, and the 1,3-butadiene and styrene were copolymerized for 2.5 hours. The polymerization was carried out under stirring at a rate of 130 rpm and a temperature within the polymerization reactor of 65° C. while the monomers were continuously fed into the polymerization reactor. The amount of 1,3-butadiene fed was 205 g, and the amount of styrene fed was 65 g.

After the 2.5-hour polymerization, 2.8 mmol of bis(diethylamino)methylvinylsilane in cyclohexane was introduced into the polymerization reactor under stirring at a rate of 130 rpm and a temperature within the polymerization reactor of 65° C., followed by stirring for 30 minutes. Next, 20 mL of a hexane solution containing 0.14 mL of methanol was introduced into the polymerization reactor, and the polymer solution was stirred for 5 minutes.

To the resulting polymer solution were added 1.8 g of 2-tert-butyl-6-(3-tert-butyl-2-hydroxy-5-methylbenzyl)-4-methylphenyl acrylate (trade name: Sumilizer GM, produced by Sumitomo Chemical Co., Ltd.) and 0.9 g of pentaerythrityl tetrakis(3-laurylthiopropionate) (trade name: Sumilizer TP-D, produced by Sumitomo Chemical Co., Ltd.). Then, Polymer 25 was recovered from the polymer solution by steam stripping. Table 5 shows the evaluation results of Polymer 25. The content of the constituent unit represented by formula (I) in the polymer, as calculated from the amounts of raw materials introduced and the amounts of raw materials fed into the polymerization reactor, was 0.006 mmol/g-polymer per unit mass of the polymer.

TABLE 5 Polymer 23 24 25 Styrene unit content (% by mass) 25 25 25 Vinyl bond content (mol %) 59 59 59 Molecular weight distribution (Mw/Mn) 1.6 1.3 1.1

The chemicals used in examples and comparative examples are described below.

-   NR1: RSS #3 -   NR2: SIR20 -   BR: Ubepol BR150B produced by Ube Industries, Ltd. -   SBR: Nipol NS116R (vinyl content: 60% by mass, styrene content: 20%     by mass) produced by Zeon Corporation -   Polymers 1 to 25: see Production Examples 1 to 25 above -   Silica: Ultrasil VN3-G (N₂SA: 175 m²/g) produced by Evonik Degussa -   Silane coupling agent 1: Si363 produced by Evonik Degussa, compound     represented by the following formula:

-   Silane coupling agent 2: NXT-Z45 (copolymer of linking unit A and     linking unit B (linking unit A: 55 mol %, linking unit B: 45 mol %))     produced by Momentive Performance Materials -   Silane coupling agent 3: Si69 produced by Evonik Degussa -   Carbon black 1: Diablack N339 (N₂SA: 96 m²/g, DBP absorption: 124     mL/100 g) produced by Mitsubishi Chemical Corporation -   Carbon black 2: Diablack N220 (N₂SA: 114 m²/g, DBP absorption: 114     mL/100 g) produced by Mitsubishi Chemical Corporation -   Amide compound 1 (processing aid 1): HT254 produced by     Schill+Seilacher GmbH, fatty acid amide processing aid (mixture of     fatty acid amide (compound represented by the formula (1):     N-(1-oxooctadecyl)sarcosine) and amino acid derivative; fatty acid     amide content: 25 to 50% by mass) -   Amide compound 2 (processing aid 2): N,N-dimethylformamide -   Oil 1: Diana process oil AH-25 produced by Idemitsu Kosan Co., Ltd. -   Oil 2: X-140 produced by JX Nippon Oil & Energy Corporation -   Oil 3: NH70-S produced by Idemitsu Kosan Co., Ltd. -   Antioxidant 1: Antigene 3C produced by Sumitomo Chemical Co., Ltd. -   Antioxidant 2: Antigene 6C produced by Sumitomo Chemical Co., Ltd. -   Stearic acid: stearic acid beads “Tsubaki” produced by NOF     Corporation -   Zinc oxide 1: zinc oxide (zinc white #1) produced by Mitsui Mining &     Smelting Co., Ltd. -   Zinc oxide 2: zinc oxide #2 produced by Mitsui Mining & Smelting     Co., Ltd. -   Wax: Sunnoc N produced by Ouchi Shinko Chemical Industrial Co., Ltd. -   Sulfur 1: sulfur powder produced by Tsurumi Chemical Industry Co.,     Ltd. -   Sulfur 2: 5% oil-treated sulfur powder produced by Tsurumi Chemical     Industry Co., Ltd. -   Vulcanization accelerator 1: Soxinol CZ produced by Sumitomo     Chemical Co., Ltd. -   Vulcanization accelerator 2: Soxinol D produced by Sumitomo Chemical     Co., Ltd.

Examples and Comparative Examples

According to each formulation shown in Tables 6 to 12, the materials other than the sulfur and vulcanization accelerators were kneaded for 5 minutes at 150° C. using a 1.7-L Banbury mixer from Kobe Steel, Ltd., to obtain a kneadate. The sulfur and vulcanization accelerators were then added to the obtained kneadate and kneading was performed using an open roll mill for 5 minutes at 80° C. to obtain an unvulcanized rubber composition. The obtained unvulcanized rubber composition was press-vulcanized for 20 minutes at 170° C. using a 0.5 mm-thick mold to obtain a vulcanized rubber composition.

In addition, the unvulcanized rubber composition was formed into a tread shape and assembled with other tire components in a tire building machine to form an unvulcanized tire. The unvulcanized tire was vulcanized for 12 minutes at 170° C. to prepare a test tire (size: 195/65R15).

Examples 1 to 5 and Comparative Examples 1 to 4

Evaluations were carried out on the obtained unvulcanized rubber compositions, vulcanized rubber compositions, and test tires by the below-mentioned testing methods. Table 6 shows the results of these tests.

(Rolling Resistance)

The rolling resistance was measured using a rolling resistance tester by running the test tire with a 15×6JJ rim at an internal pressure of 230 kPa, a load of 3.43 kN, and a speed of 80 km/h. Based on the equation below, the rolling resistance of the tire of each composition was expressed as an index (rolling resistance index) relative to that of Comparative Example 1 regarded as 100. A larger index indicates a lower rolling resistance, which in turn indicates better fuel economy. (Rolling resistance index)=(Rolling resistance in Comparative Example 1)/(Rolling resistance of each composition)×100 (Wet-grip Performance)

The produced test tires were mounted on all the wheels of a vehicle (Japanese FF car, 2000 cc), and the braking distance with an initial speed of 100 km/h was determined on a wet asphalt road surface. Based on the equation below, the wet-skid performance (wet-grip performance) of the tires of each composition was expressed as an index (wet-grip performance index) relative to that of Comparative Example 1 regarded as 100. A larger index indicates better wet-grip performance. (Wet-grip performance index)=(Braking distance of Comparative Example 1)/(Braking distance of each composition)×100 (Abrasion Resistance)

The produced test tires were mounted on all the wheels of a vehicle (Japanese FF car, 2000 cc), and the vehicle was driven. The change in the groove depth of the tread pattern before and after 30000 km running was determined. Based on the equation below, the change in the groove depth of the tires of each composition was expressed as an index (abrasion resistance index) relative to that of Comparative Example 1 regarded as 100. A larger index indicates better abrasion resistance. (Abrasion resistance index)=(Groove depth change of standard comparative example)/(Groove depth change of each composition)×100 (Handling Stability)

The produced test tires were mounted on all the wheels of a vehicle (Japanese FF car, 2000 cc), and the vehicle was driven. The handling stability was evaluated based on sensory evaluation by a driver. Relative evaluation was made on a scale of 1 to 10, where the results of the standard comparative example were given 6. A larger handling stability score indicates better handling stability.

(Rubber Texture)

The unvulcanized rubber composition was extrusion-formed into a rubber sheet. The shape of the obtained sheet was visually observed and evaluated based on the following criteria. A less favorable shape of the sheet indicates poorer workability (processability).

Very good: The sheet shape is very good.

Good: The sheet shape is good.

Poor: The sheet shape is bad.

Very poor: The sheet shape is significantly bad.

(Mooney Viscosity)

The prepared unvulcanized rubber composition was measured for Mooney viscosity at 130° C. according to the method for determining the Mooney viscosity specified in JIS K6300-1:2001. Based on the equation below, the Mooney viscosity (ML₁₊₄) of each composition was expressed as an index (Mooney viscosity index) relative to the Mooney viscosity (ML₁₊₄) of Comparative Example 1 regarded as 100. A larger index indicates a lower Mooney viscosity, which in turn indicates better processability. (Mooney viscosity index)=(ML₁₊₄ of Comparative Example 1)/(ML₁₋₄ of each composition)×100

TABLE 6 Example Comparative Example 1 2 3 4 5 1 2 3 4 Composition NR1 20 20 20 20 20 20 20 20 20 (parts BR 20 20 20 20 20 20 20 20 20 by mass) Polymer 1 60 60 — — 60 — 60 — — Polymer 2 — — 60 60 — — — — — Polymer 3 (unmodified SBR) — — — — — 60 — 60 60 Silica 60 60 60 60 60 60 60 60 60 Silane coupling agent 1 4.8 4.8 4.8 4.8 — 4.8 4.8 — 4.8 Silane coupling agent 2 — — — — 4.8 — — — — Silane coupling agent 3 — — — — — — — 4.8 — Carbon black 1 5 5 5 5 5 5 5 5 5 Amide compound 1 3 1 3 1 3 — — 1 1 Oil 1 8 8 8 8 8 8 8 8 8 Antioxidant 1 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 Stearic acid 2 2 2 2 2 2 2 2 2 Zinc oxide 1 3 3 3 3 3 3 3 3 3 Wax 1 1 1 1 1 1 1 1 1 Sulfur 1 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 Vulcanization accelerator 1 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 Vulcanization accelerator 2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 Evaluation Rolling resistance index 128 130 125 127 130 100 106 95 98 Wet-grip performance index 124 122 122 119 126 100 108 94 102 Abrasion resistance index 120 122 117 119 120 100 95 94 98 Handling stability 6.5 6.5 6.5 6.5 6.5 6 6 5.5 5.5 Rubber texture Very Good Very Good Very Poor Very Good Good good good good poor Mooney viscosity index 85 94 86 94 82 100 80 108 103

As shown in Table 6, in the examples which used a combination of silica, a compound (amide compound 1) represented by the above formula (1), and a polymer (polymer 1 or 2) containing a constituent unit based on a conjugated diene and a constituent unit represented by the above formula (I) and having a terminal modified with a compound represented by the above formula (II), the fuel economy, wet-grip performance, abrasion resistance, and processability were enhanced in a balanced manner as compared with the comparative examples. Moreover, good handling stability and acceptable Mooney viscosity were achieved in the examples.

Examples 6 to 9 and Comparative Examples 5 to 8

Evaluations were carried out on the obtained unvulcanized rubber compositions and vulcanized rubber compositions by the below-mentioned testing methods. Table 7 shows the results of these tests.

(Mooney Viscosity)

The unvulcanized rubber composition was measured for Mooney viscosity at 130° C. according to the method for determining the Mooney viscosity specified in JIS K6300-1:2001. Based on the equation below, the Mooney viscosity (ML₁₊₄) of each composition was expressed as an index (Mooney viscosity index) relative to the Mooney viscosity (ML₁₊₄) of Comparative Example 5 regarded as 100. A larger index indicates a lower Mooney viscosity, which in turn indicates better processability. (Mooney viscosity index)=(ML₁₊₄ of Comparative Example 5)/(ML₁₊₄ of each composition)×100 (Rubber Texture)

The unvulcanized rubber composition was extrusion-formed into a rubber sheet. The shape of the obtained sheet was visually observed and evaluated based on the following criteria. A less favorable shape of the sheet indicates poorer workability (processability).

Very good: The sheet shape is very good.

Good: The sheet shape is good.

Poor: The sheet shape is bad.

(tan δ)

The loss tangent (tan δ) of each composition (vulcanized rubber composition) was determined with a viscoelasticity spectrometer VES (produced by Iwamoto Seisakusyo Co., Ltd.) at a temperature of 50° C., an initial strain of 10%, a dynamic strain of 2%, and a frequency of 10 Hz. Based on the equation below, the obtained value of tan δ was expressed as an index relative to the tan δ in Comparative Example 5 regarded as 100. A larger index indicates a lower rolling resistance, which in turn indicates better fuel economy. (tan δ index)=(tan δ in Comparative Example 5)/(tan δ of each composition)×100 (Abrasion Test)

The vulcanized rubber composition was measured for Lambourn abrasion with a Lambourn abrasion tester at a temperature of 20° C., a slip ratio of 20%, and a test time of 2 minutes. Then, the volume loss was calculated from the measured Lambourn abrasion amount, and expressed as an index relative to the volume loss of Comparative Example 5 regarded as 100, based on the equation below. A larger index indicates better abrasion resistance. (Abrasion resistance index)=(Volume loss of Comparative Example 5)/(Volume loss of each composition)×100 (Wet Test)

The wet-grip performance was evaluated using a flat belt abrasion tester (FR5010, produced by Ueshima Seisakusho Co., Ltd.). The vulcanized rubber composition was shaped into a cylindrical sample (width: 20 mm, diameter: 100 mm). The test was carried out at a speed of 20 km/hour, a load of 4 kgf, and a road surface temperature of 20° C. while the slip ratio of the sample on a road surface was varied between 0 and 50%. The maximum friction coefficient detected during the test was read, and expressed as an index relative to the maximum friction coefficient of Comparative Example 5 regarded as 100, based on the equation below. A larger index indicates better wet-grip performance. (Wet-grip performance index)=(Maximum friction coefficient of each composition)/(Maximum friction coefficient of Comparative Example 5)×100

TABLE 7 Example Comparative Example 6 7 8 9 5 6 7 8 Composition NR1 20 20 20 20 20 20 20 20 (parts BR 20 30 20 20 20 20 20 20 by mass) SBR — — — — 60 — 60 60 Polymer 4 60 50 60 — — 60 — — Polymer 5 — — — 60 — — — — Silica 75 75 75 75 75 75 75 75 Silane coupling agent 3 6 6 6 6 6 6 6 6 Carbon black 1 5 5 5 5 5 5 5 5 Oil 2 20 20 20 20 20 20 20 20 Antioxidant 1 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 Stearic acid 2 2 2 2 2 2 2 2 Zinc oxide 1 2 2 2 2 2 2 2 2 Amide compound 1 2.5 2.5 2 2.5 — — 2.5 5 Sulfur 1 2 2 2 2 2 2 2 2 Vulcanization accelerator 1 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 Vulcanization accelerator 2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 Evaluation Mooney viscosity index 115 120 118 116 100 80 113 130 Rubber texture Very Very Very Very Good Good Very Very good good good good good good tan δ index 112 110 113 110 100 106 98 97 Abrasion resistance index 105 103 104 102 100 95 101 103 Wet-grip performance index 103 103 102 102 100 98 99 98

As shown in Table 7, in the examples which used a combination of silica, a compound (amide compound 1) represented by the above formula (1), and a polymer (polymer 4 or 5) containing a constituent unit based on a conjugated diene and a constituent unit represented by the above formula (I) and having a terminal modified with a compound containing a group represented by the above formula (III), the fuel economy, wet-grip performance, abrasion resistance, and processability were enhanced synergistically and achieved at high levels in a balanced manner as compared with the comparative examples.

Examples 10 to 16 and Comparative Examples 9 to 23

Evaluations were carried out on the obtained unvulcanized rubber compositions and test tires by the below-mentioned testing methods. Tables 8 and 9 show the results of these tests.

(Mooney Viscosity)

The unvulcanized rubber composition was measured for Mooney viscosity at 130° C. according to the method for determining the Mooney viscosity specified in JIS K6300-1:2001. Based on the equation below, the Mooney viscosity (ML₁₊₄) of each composition was expressed as an index (Mooney viscosity index) relative to the Mooney viscosity (ML₁₊₄) of Comparative Example 16 regarded as 100. A larger index indicates a lower Mooney viscosity, which in turn indicates better processability. (Mooney viscosity index)=(ML₁₊₄ of Comparative Example 16)/(ML₁₊₄ of each composition)×100 (Rubber Sheet Texture)

The unvulcanized rubber composition was extrusion-formed into a rubber sheet. The surface properties of the obtained sheet were visually observed and evaluated based on the following criteria. Better sheet properties indicate better workability.

Very good: The sheet texture is very good.

Good: The sheet texture is good.

Poor: The sheet texture is slightly bad.

Very poor: The sheet texture is very bad.

(Rolling Resistance)

The rolling resistance was measured using a rolling resistance tester by running the test tire with a 15×6JJ rim at an internal pressure of 230 kPa, a load of 3.43 kN, and a speed of 80 km/h. The rolling resistance of the tire of each composition was expressed as an index relative to that of Comparative Example 16 regarded as 100. A larger index indicates a lower rolling resistance, which in turn indicates better fuel economy.

(Wet-grip Performance)

The produced test tires were mounted on all the wheels of a vehicle (Japanese FF car, 2000 cc), and the braking distance with an initial speed of 100 km/h was determined on a wet asphalt road surface. The results were expressed as an index. A larger index indicates better wet-skid performance (wet-grip performance). The index was determined based on the following equation. (Wet-grip performance index)=(Braking distance of Comparative Example 16)/(Braking distance of each composition)×100 (Abrasion Resistance)

The produced test tires were mounted on all the wheels of a vehicle (Japanese FF car, 2000 cc), and the vehicle was driven. The change in the groove depth of the tread pattern before and after 35000 km running was determined. Based on the equation below, the change in the groove depth of each composition was expressed as an index (abrasion resistance index) relative to that of Comparative Example 16 regarded as 100. A larger index indicates better abrasion resistance. (Abrasion resistance index)=(Groove depth change of Comparative Example 16)/(Groove depth change of each composition)×100

TABLE 8 Comparative Example 9 10 11 12 13 14 15 16 17 18 19 Composition NR1 20 20 20 20 20 20 20 20 20 20 20 (parts BR 20 20 20 20 20 20 20 20 20 20 20 by mass) Polymer 6 60 — — — 20 60 — — — — — Polymer 7 — 60 — — — — — — — — — Polymer 8 — — 60 — — — — — — — — Polymer 9 — — — 60 — — — — — — — Polymer 10 — — — — 40 — — — 60 — — Polymer 11 — — — — — — — — — 60 — Polymer 12 — — — — — — — — — — 60 Polymer 13 — — — — — — — 60 — — — Polymer 14 — — — — — — 60 — — — — Silica 75 75 75 75 75 50 75 75 75 75 75 Silane coupling agent 3 6 6 6 6 6 4 6 6 6 6 6 Carbon black 5 5 5 5 5 5 5 5 5 5 5 Oil 2 20 20 20 20 20 5 20 20 20 20 20 Antioxidant 1 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 Stearic acid 2 2 2 2 2 2 2 2 2 2 2 Zinc oxide 1 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 Wax 1 1 1 1 1 1 1 1 1 1 1 Amide compound 1 — — — — — — — — — — — Sulfur 1 2 2 2 2 2 2 2 2 2 2 2 Vulcanization accelerator 1 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 Vulcanization accelerator 2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 Evaluation Mooney viscosity index 69 72 70 66 92 60 69 100 100 101 98 Rubber sheet texture Very Very Very Very Poor Very Very Poor Poor Poor Poor poor poor poor poor poor poor Rolling resistance index 136 138 140 140 115 137 128 100 109 111 113 Wet-grip performance index 139 140 142 144 120 140 131 100 118 121 122 Abrasion resistance index 120 121 125 127 110 119 115 100 109 110 112

TABLE 9 Example Comparative Example 10 11 12 13 14 15 16 20 21 22 23 Composition NR1 20 20 20 20 20 20 20 20 20 20 20 (parts BR 20 20 20 20 20 20 20 20 20 20 20 by mass) Polymer 6 60 — — — 20 60 — — — — — Polymer 7 — 60 — — — — — — — — — Polymer 8 — — 60 — — — — — — — — Polymer 9 — — — 60 — — — — — — — Polymer 10 — — — — 40 — — — 60 — — Polymer 11 — — — — — — — — — 60 — Polymer 12 — — — — — — — — — — 60 Polymer 13 — — — — — — — 60 — — — Polymer 14 — — — — — — 60 — — — — Silica 75 75 75 75 75 50 75 75 75 75 75 Silane coupling agent 3 6 6 6 6 6 4 6 6 6 6 6 Carbon black 1 5 5 5 5 5 5 5 5 5 5 5 Oil 2 20 20 20 20 20 5 20 20 20 20 20 Antioxidant 1 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 Stearic acid 2 2 2 2 2 2 2 2 2 2 2 Zinc oxide 1 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 Wax 1 1 1 1 1 1 1 1 1 1 1 Amide compound 1 4 4 4 4 4 4 4 4 4 4 4 Sulfur 1 2 2 2 2 2 2 2 2 2 2 2 Vulcanization accelerator 1 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 Vulcanization accelerator 2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 Evaluation Mooney viscosity index 102 105 101 99 126 90 100 125 127 128 124 Rubber sheet texture Good Good Good Good Very Good Good Very Very Very Very good good good good good Rolling resistance index 143 146 147 147 123 145 136 103 111 112 114 Wet-grip performance index 140 141 142 146 121 141 131 101 120 122 125 Abrasion resistance index 121 124 125 128 111 120 116 102 110 113 114

As shown in Tables 8 and 9, in the examples which used a combination of silica, a compound (amide compound 1) represented by the above formula (1), and a polymer (polymer 6, 7, 8, 9, or 14) containing a constituent unit based on a conjugated diene and a constituent unit represented by the above formula (I) and having a terminal modified with a compound represented by the above formula (IV), the fuel economy, wet-grip performance, abrasion resistance, and processability were enhanced in a balanced manner and, in particular, the fuel economy and processability were greatly enhanced as compared with the comparative examples.

Examples 17 to 24 and Comparative Examples 24 to 33

Evaluations were carried out on the obtained unvulcanized rubber compositions, vulcanized rubber compositions, and test tires by the below-mentioned testing methods. Tables 10 and 11 show the results of these tests.

(tan δ)

A strip test sample (width: 1 mm or 2 mm, length: 40 mm) was punched out of the sheet-shaped vulcanized rubber composition and used for the test. The tan δ of the test sample was determined with a spectrometer (produced by Ueshima Seisakusho Co., Ltd.) at a dynamic strain amplitude of 1%, a frequency of 10 Hz, and a temperature of 50° C. The reciprocal of the value of tan δ was expressed as an index relative to that of Comparative Example 24 regarded as 100. A larger index indicates a lower rolling resistance, which in turn indicates better fuel economy.

(Rolling Resistance)

The rolling resistance was measured using a rolling resistance tester by running the test tire with a 15×6JJ rim at an internal pressure of 230 kPa, a load of 3.43 kN, and a speed of 80 km/h. The rolling resistance of the tire of each composition was expressed as an index relative to that of Comparative Example 24 regarded as 100. A larger index indicates a lower rolling resistance, which in turn indicates better fuel economy.

(Wet-grip Performance)

The test tires were mounted on all the wheels of a vehicle (Japanese FF car, 2000 cc), and the braking distance with an initial speed of 100 km/h was determined on a wet asphalt road surface. The results were expressed as an index. A larger index indicates better wet-skid performance (wet-grip performance). The index was determined based on the following equation. (Wet-grip performance index)=(Braking distance of Comparative Example 24)/(Braking distance of each composition)×100 (LAT Abrasion Test)

The volume loss of each vulcanized rubber composition was measured with a LAT tester (Laboratory Abrasion and Skid Tester) at a load of 50 N, a speed of 20 km/h, and a slip angle of 5 degrees. The values (abrasion resistance indices) in Tables 10 and 11 are relative values compared to the volume loss of Comparative Example 24 which was set to 100. A larger value indicates better abrasion resistance.

(Mooney Viscosity)

The unvulcanized rubber composition was measured for Mooney viscosity at 130° C. according to the method for determining the Mooney viscosity specified in JIS K6300-1:2001. Based on the equation below, the Mooney viscosity (ML₁₊₄) of each composition was expressed as an index (Mooney viscosity index) relative to the Mooney viscosity (ML₁₊₄) of Comparative Example 24 regarded as 100. A larger index indicates a lower Mooney viscosity, which in turn indicates better processability. (Mooney viscosity index)=(ML₁₊₄ of Comparative Example 24)/(ML₁₊₄ of each composition)×100 (Rubber Sheet Texture)

The unvulcanized rubber composition was extrusion-formed into a rubber sheet. The surface properties of the obtained sheet were visually observed and evaluated based on the following criteria. Better sheet properties indicate better workability.

Very good: The sheet texture is very good.

Good: The sheet texture is good.

Poor: The sheet texture is slightly bad.

Very poor: The sheet texture is very bad.

TABLE 10 Example 17 18 19 20 21 22 23 24 Composition NR1 20 20 20 20 20 20 20 20 (parts BR 20 20 20 20 20 20 20 20 by mass) Polymer 15 60 — 20 — — — — 60 Polymer 16 — 60 40 60 — — — — Polymer 17 — — — — — — — — Polymer 18 — — — — — — — — Polymer 19 — — — — — — — — Polymer 20 — — — — — — — — Polymer 21 — — — — 60 — — _(—) Polymer 22 — — — — — 60 60 — Silica 75 75 75 75 75 75 75 75 Silane coupling agent 3 6 6 6 6 6 6 6 6 Carbon black 2 5 5 5 5 5 5 5 5 Oil 2 20 20 20 20 20 20 20 20 Antioxidant 1 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 Stearic acid 2 2 2 2 2 2 2 2 Zinc oxide 1 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 Wax 1 1 1 1 1 1 1 1 Amide compound 2 — — — — — — 2.5 2.5 Amide compound 1 2.5 2.5 2.5 4.0 2.5 2.5 — — Sulfur 1 2 2 2 2 2 2 2 2 Vulcanization accelerator 1 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 Vulcanization accelerator 2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 Evaluation tan δ index 140 143 141 134 132 135 123 128 Rolling resistance index 130 132 131 125 122 125 116 123 Wet-grip performance index 135 139 136 129 129 133 126 129 Abrasion resistance index 118 122 119 110 110 115 111 113 Mooney viscosity index 101 100 100 103 104 103 103 101 Rubber sheet texture Good Good Good Good Good Good Good Good

TABLE 11 Comparative Example 24 25 26 27 28 29 30 31 32 33 Composition NR1 20 20 20 20 20 20 20 20 20 20 (parts BR 20 20 20 20 20 20 20 20 20 20 by mass) Polymer 15 — 60 — — — — — — — — Polymer 16 — — — — — — — — — — Polymer 17 — — — 60 — — — 60 — — Polymer 18 — — — — 60 — — — 60 — Polymer 19 — — — — — 60 — — — 60 Polymer 20 60 — 60 — — — 60 — — — Polymer 21 — — — — — — — — — — Polymer 22 — — — — — — — — — — Silica 75 75 75 75 75 75 75 75 75 75 Silane coupling agent 3 6 6 6 6 6 6 6 6 6 6 Carbon black 2 5 5 5 5 5 5 5 5 5 5 Oil 2 20 20 20 20 20 20 20 20 20 20 Antioxidant 1 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 Stearic acid 2 2 2 2 2 2 2 2 2 2 Zinc oxide 1 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 Wax 1 1 1 1 1 1 1 1 1 1 Amide compound 2 — — 2.5 2.5 2.5 2.5 — — — — Amide compound 1 — — — — — — 2.5 2.5 2.5 2.5 Sulfur 1 2 2 2 2 2 2 2 2 2 2 Vulcanization accelerator 1 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 Vulcanization accelerator 2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 Evaluation tan δ index 100 130 98 116 120 108 101 119 123 111 Rolling resistance index 100 125 98 107 110 104 101 110 113 107 Wet-grip performance index 100 128 101 116 121 109 105 120 125 113 Abrasion resistance index 100 115 98 118 112 110 101 121 115 113 Mooney viscosity index 100 70 115 105 102 108 115 105 102 108 Rubber sheet texture Poor Very Very Good Good Good Very Good Good Good poor good good

As shown in Tables 10 and 11, in the examples which used a combination of silica, a compound (amide compound 1 or 2) represented by the above formula (1), and a polymer (polymer 15, 16, 21, or 22) containing a constituent unit based on a conjugated diene and a constituent unit represented by the above formula (I) and having a terminal modified with a silicon compound including a silicon compound containing a group represented by the above formula (V) and/or a group represented by the above formula (VI), the fuel economy, wet-grip performance, abrasion resistance, and processability were enhanced in a balanced manner as compared with the comparative examples. In particular, these properties tend to be greatly enhanced in the examples in which the amide compound 1 was mixed.

Examples 25 to 26 and Comparative Examples 34 to 36

Evaluations were carried out on the obtained unvulcanized rubber compositions, vulcanized rubber compositions, and test tires by the below-mentioned testing methods. Table 12 shows the results of these tests.

(Rubber Texture)

The unvulcanized rubber composition was extrusion-formed into a rubber sheet. The properties of the obtained sheet were visually observed and evaluated based on the following criteria. Better sheet properties indicate better workability (processability).

Very good: The sheet shape is very good.

Good: The sheet shape is good.

Poor: The sheet has irregularities.

Very poor: The sheet is poorly shaped.

(tan δ)

A strip test sample (width: 1 mm or 2 mm, length: 40 mm) was punched out of the sheet-shaped vulcanized rubber composition and used for the test. The tan δ of the test sample was determined with a spectrometer (produced by Ueshima Seisakusho Co., Ltd.) at a dynamic strain amplitude of 1%, a frequency of 10 Hz, and a temperature of 50° C. The reciprocal of the value of tan δ was expressed as an index relative to that of Comparative Example 36 regarded as 100. A larger value indicates a lower rolling resistance, which in turn indicates better fuel economy.

(Rolling Resistance)

The rolling resistance was measured using a rolling resistance tester by running the test tire with a 15×6JJ rim at an internal pressure of 230 kPa, a load of 3.43 kN, and a speed of 80 km/h. The rolling resistance of the tire of each composition was expressed as an index relative to that of Comparative Example 36 regarded as 100. A larger index indicates better performance (better fuel economy).

(Wet-grip Performance)

The test tires were mounted on all the wheels of a vehicle (Japanese FF car, 2000 cc), and the braking distance with an initial speed of 100 km/h was determined on a wet asphalt road surface. The results were expressed as an index. A larger index indicates better wet-skid performance (wet-grip performance). The index was determined based on the following equation. (Wet-grip performance index)=(Braking distance of Comparative Example 36)/(Braking distance of each composition)×100 (Mooney Viscosity)

The unvulcanized rubber composition was measured for Mooney viscosity at 130° C. according to the method for determining the Mooney viscosity specified in JIS K6300-1:2001. Based on the equation below, the Mooney viscosity (ML₁₊₄) of each composition was expressed as an index (Mooney viscosity index) relative to the Mooney viscosity (ML₁₊₄) of Comparative Example 3 regarded as 100. A smaller index indicates a lower Mooney viscosity, which in turn indicates better processability. (Mooney viscosity index)=(ML₁₊₄ of each example or comparative example)/(ML₁₊₄ of Comparative Example 3)×100 (LAT Abrasion Test)

The volume loss of each vulcanized rubber composition was measured with a LAT tester (Laboratory Abrasion and Skid Tester) at a load of 50 N, a speed of 20 km/h, and a slip angle of 5 degrees. The values (abrasion resistance indices) in Table 12 are relative values compared to the volume loss of Comparative Example 36 which was set to 100. A larger value indicates better abrasion resistance.

TABLE 12 Example Comparative Example 25 26 34 35 36 Composition NR2 20 20 20 20 20 (parts BR 20 20 20 20 20 by mass) Polymer 23 60 — — 60 — Polymer 24 — 60 — — — Polymer 25 — — 60 — 60 Silica 75 75 75 75 75 Silane coupling agent 2 6 6 6 6 6 Carbon black 2 5 5 5 5 5 Oil 3 20 20 20 20 20 Antioxidant 2 1.5 1.5 1.5 1.5 1.5 Stearic acid 2 2 2 2 2 Zinc oxide 2 3 3 3 3 3 Amide compound 1 2 2 2 — — Sulfur 2 2 2 2 2 2 Vulcanization accelerator 1 1.8 1.8 1.8 1.8 1.8 Vulcanization accelerator 2 1.2 1.2 1.2 1.2 1.2 Evaluation Rubber texture Very Good Poor Very Very good poor poor tan δ index 130 125 120 110 100 Rolling resistance index 130 130 120 110 100 Wet-grip performance index 130 130 120 100 100 Mooney viscosity index 80 90 95 100 100 Abrasion resistance index 110 105 100 100 100

As shown in Table 12, in the examples which used a combination of silica, a compound (amide compound 1) represented by the above formula (1), and a polymer (polymer 23 or 24) containing a constituent unit based on a conjugated diene and a constituent unit represented by the above formula (I) and having a terminal modified with a compound containing a group represented by the above formula (VII), the fuel economy, wet-grip performance, abrasion resistance, and processability were enhanced in a balanced manner and, in particular, the wet-grip performance, abrasion resistance, and processability were greatly enhanced as compared with the comparative examples.

In contrast, the processability was poor in Comparative Example 34 in which the amide compound 1 was mixed, but the polymer 1 or 2 was not used. Not only the processability but also other properties were poor in Comparative Examples 35 and 36 in which the amide compound 1 was not mixed. 

The invention claimed is:
 1. A rubber composition, comprising a rubber component, silica, and a processing aid compound represented by formula (1) below, wherein the rubber component contains, based on 100% by mass of the rubber component, not less than 5% by mass of a conjugated diene polymer containing a constituent unit based on a conjugated diene and a constituent unit represented by formula (I) below, at least one terminal of the polymer being modified with at least one compound selected from the group consisting of a compound represented by formula (II) below, a compound containing a group represented by formula (III) below, a compound represented by formula (IV) below, a silicon compound containing at least one of a group represented by formula (V) below and a group represented by formula (VI) below, and a compound containing a group represented by formula (VII) below, wherein the silica is present in an amount of 5 to 150 parts by mass per 100 parts by mass of the rubber component, formula (I):

wherein X¹, X², and X³ each independently represent a group represented by formula (Ia) below, a hydroxy group, a hydrocarbyl group, or a substituted hydrocarbyl group, and at least one of X¹, X², and X³ is a hydroxy group or a group represented by the following formula (Ia):

wherein R¹ and R² each independently represent a C₁₋₆ hydrocarbyl group, a C₁₋₆ substituted hydrocarbyl group, a silyl group, or a substituted silyl group, and R¹ and R² may be bonded to each other to form a cyclic structure together with the nitrogen atom; formula (II):

wherein n represents an integer of 1 to 10; R¹¹, R¹², and R¹³ each independently represent a C₁₋₄ hydrocarbyl group or a C₁₋₄ hydrocarbyloxy group, and at least one of R¹¹, R¹², and R¹³ is the hydrocarbyloxy group; and A¹ represents a nitrogen atom-bearing functional group; formula (III):

wherein p represents an integer of 0 or 1; T represents a C₁₋₂₀ hydrocarbylene group or a C₁₋₂₀ substituted hydrocarbylene group; and A² represents a nitrogen atom-bearing functional group; formula (IV):

wherein g represents an integer of 1 to 10; R²¹ represents a hydrogen atom, a C₁₋₆ hydrocarbyl group, or a C₁₋₆ substituted hydrocarbyl group; A³ represents an oxygen atom or the following group: —NR²²— where R²² represents a hydrogen atom or a C₁₋₁₀ hydrocarbyl group; and A⁴ represents a functional group bearing at least one of a nitrogen atom and an oxygen atom; formulas (V), (VI) and (VII):

wherein w represents an integer of 1 to 11, and A⁵ represents a nitrogen atom-bearing functional group; formula (1):

wherein R¹⁰¹ represents a hydrogen atom, a branched or unbranched C₁₋₃₀ alkyl group, a branched or unbranched C₂₋₃₀ alkenyl group, a branched or unbranched C₆₋₃₀ aryl group, or a hydroxy group; R¹⁰² and R¹⁰³ are the same as or different from each other and each represent a hydrogen atom, a branched or unbranched C₁₋₃₀ alkyl group, a branched or unbranched C₂₋₃₀ alkenyl group, a branched or unbranched C₂₋₃₀ alkynyl group, a branched or unbranched C₆₋₃₀ aryl group, or a group represented by formula (2) below, wherein a hydrogen atom of the alkyl group, alkenyl group, alkynyl group, or aryl group may be substituted by a hydroxy group or a carboxyl group; a pair of R¹⁰¹ and R¹⁰², a pair of R¹⁰¹ and R¹⁰³, or a pair of R¹⁰² and R¹⁰³ may form a cyclic structure; and d₁ is zero,

wherein R¹⁰⁴ represents a branched or unbranched C₁₋₃₀ alkylene group; R¹⁰⁵ represents a hydrogen atom, a branched or unbranched C₁₋₃₀ alkyl group, a branched or unbranched C₂₋₃₀ alkenyl group, a branched or unbranched C₆₋₃₀ aryl group, or a hydroxy group; and d₂ represents an integer of 0 to
 10. 2. The rubber composition according to claim 1, wherein R¹ and R² in formula (Ia) are C₁₋₆ hydrocarbyl groups.
 3. The rubber composition according to claim 1, wherein two of X¹, X², and X³ in formula (I) are selected from a group represented by formula (Ia) and a hydroxy group.
 4. The rubber composition according to claim 1, wherein A¹ in formula (II) is a group represented by the following formula (IIa):

wherein R¹⁴ and R¹⁵ each independently represent a C₁₋₆ group optionally containing at least one atom selected from the group consisting of a nitrogen atom, an oxygen atom, and a silicon atom, R¹⁴ and R¹⁵ may be bonded to each other to form a cyclic structure together with the nitrogen atom, and R¹⁴ and R¹⁵ may form a single group bonded to the nitrogen via a double bond.
 5. The rubber composition according to claim 1, wherein the group represented by formula (III) is a group represented by the following formula (IIIa):


6. The rubber composition according to claim 5, wherein the compound containing a group represented by formula (III) is at least one compound selected from the group consisting of a compound represented by formula (IIIa-1) below, a compound represented by formula (IIIa-2) below, and a compound represented by formula (IIIa-3) below,

wherein R³¹ represents a hydrogen atom, a C₁₋₁₀ hydrocarbyl group, a C₁₋₁₀ substituted hydrocarbyl group, or a heterocyclic group containing at least one of a nitrogen atom and an oxygen atom as a heteroatom; and R³² and R³³ each independently represent a C₁₋₁₀ group optionally containing at least one atom selected from the group consisting of a nitrogen atom, an oxygen atom, and a silicon atom, R³² and R³³ may be bonded to each other to form a cyclic structure together with the nitrogen atom, and R³² and R³³ may form a single group bonded to the nitrogen via a double bond;

wherein e represents an integer of 0 to 10, and R³⁴ and R³⁵ each independently represent a C₁₋₂₀ hydrocarbyl group or a C₁₋₂₀ substituted hydrocarbyl group;

wherein f represents an integer of 0 to 10, and R³⁶ represents a C₁₋₂₀ hydrocarbyl group or a C₁₋₂₀ substituted hydrocarbyl group.
 7. The rubber composition according to claim 1, wherein the compound containing a group represented by formula (III) is a compound represented by the following formula (IIIb-1):

wherein R³⁷ represents a hydrogen atom, a C₁₋₁₀ hydrocarbyl group, a C₁₋₁₀ substituted hydrocarbyl group, or a heterocyclic group containing at least one of a nitrogen atom and an oxygen atom as a heteroatom; R³⁸ and R³⁹ each independently represent a C₁₋₁₀ group optionally containing at least one atom selected from the group consisting of a nitrogen atom, an oxygen atom, and a silicon atom, R³⁸ and R³⁹ may be bonded to each other to form a cyclic structure together with the nitrogen atom, and R³⁸ and R³⁹ may form a single group bonded to the nitrogen via a double bond; and T represents a C₁₋₂₀ hydrocarbylene group or a C₁₋₂₀ substituted hydrocarbylene group.
 8. The rubber composition according to claim 7, wherein the compound represented by formula (IIIb-1) is at least one compound selected from the group consisting of a compound represented by formula (IIIb-1-1) below, and a compound represented by formula (IIIb-1-2) below,

wherein r represents an integer of 1 or 2; and Y¹ represents a nitrogen atom-bearing functional group that is a substituent on the benzene ring, and when a plurality of Y¹'s are present, the plurality of Y¹'s may be the same as or different from one another;

wherein s represents an integer of 1 or 2; t represents an integer of 0 to 2; Y² and Y³ each represent a nitrogen atom-bearing functional group that is a substituent on the benzene ring, and when a plurality of Y²'s are present, the plurality of Y²'s may be the same as or different from one another, and when a plurality of Y³'s are present, the plurality of Y³'s may be the same as or different from one another.
 9. The rubber composition according to claim 1, wherein A⁴ in formula (IV) is a hydroxy group or a group represented by the following formula (IVa):

wherein R²³ and R²⁴ each independently represent a C₁₋₆ group optionally containing at least one atom selected from the group consisting of a nitrogen atom, an oxygen atom, and a silicon atom, R²³ and R²⁴ may be bonded to each other to form a cyclic structure together with the nitrogen atom, and R²³ and R²⁴ may form a single group bonded to the nitrogen via a double bond.
 10. The rubber composition according to claim 1, wherein the silicon compound contains a group represented by the following formula (VIII):

wherein R⁴¹, R⁴², and R⁴³ each independently represent a C₁₋₄ hydrocarbyl group or a C₁₋₄ hydrocarbyloxy group, and at least one of R⁴¹, R⁴², and R⁴³ is the hydrocarbyloxy group.
 11. The rubber composition according to claim 1, wherein the silicon compound contains a group represented by the following formula (Va):

wherein h represents an integer of 1 to 10; and R⁴⁴, R⁴⁵, and R⁴⁶ each independently represent a C₁₋₄ hydrocarbyl group or a C₁₋₄ hydrocarbyloxy group, and at least one of R⁴⁴, R⁴⁵, and R⁴⁶ is the hydrocarbyloxy group.
 12. The rubber composition according to claim 1, wherein the compound containing a group represented by formula (VII) is a compound represented by the following formula (VII-1):

wherein z represents an integer of 0 to 10; R⁷¹ represents a C₁₋₅ hydrocarbyl group; R⁷², R⁷³, R⁷⁴ and R⁷⁵ each independently represent a hydrogen atom, a C₁₋₅ hydrocarbyl group, a C₁₋₅ substituted hydrocarbyl group, or a C₁₋₅ hydrocarbyloxy group, and when a plurality of R⁷²'s and a plurality of R⁷³'s are present, the plurality of R⁷²'s and the plurality of R⁷³'s may be the same as or different from one another; and R⁷⁶ and R⁷⁷ each independently represent a C₁₋₆ group optionally containing at least one atom selected from the group consisting of a nitrogen atom, an oxygen atom, and a silicon atom, R⁷⁶ and R⁷⁷ may be bonded to each other to form a cyclic structure together with the nitrogen atom, and R⁷⁶ and R⁷⁷ may form a single group bonded to the nitrogen via a double bond.
 13. The rubber composition according to claim 12, wherein one of R⁷⁴ and R⁷⁵ in formula (VII-1) is a hydrogen atom.
 14. The rubber composition according to claim 1, wherein the conjugated diene polymer has a vinyl bond content of at least 10 mol % but not more than 80 mol % per 100 mol % of the constituent unit based on a conjugated diene.
 15. The rubber composition according to claim 1, comprising at least one of natural rubber and butadiene rubber.
 16. The rubber composition according to claim 1, wherein the silica has a nitrogen adsorption specific surface area of 40 to 400 m²/g.
 17. The rubber composition according to claim 1, wherein an amount of the processing aid compound represented by formula (1) is 0.1 to 20 parts by mass per 100 parts by mass of silica.
 18. The rubber composition according to claim 1, which is for use as a rubber composition for a tread.
 19. A pneumatic tire formed from the rubber composition according to claim
 1. 